Formation of field-tunable silicon carbide defect qubits with optically transparent electrodes and silicon oxide surface passivation

Abstract

A method includes depositing a layer of silicon oxide onto a layer of silicon carbide; ion implanting the layer of silicon carbide, annealing the ion implanted layer of silicon carbide to produce defects within the layer of silicon carbide, performing photolithography using a mask layer on regions of the layer of silicon carbide to define regions for electrode deposition, removing the layer of silicon oxide from the layer of silicon carbide in the one or more regions for electrode deposition, forming one or more electrodes by depositing indium tin oxide (ITO) in each of the regions for electrode deposition, performing a first lift-off operation to remove the mask layer surrounding the electrodes, depositing a passivation and gate silicon oxide layer on top of the layer of silicon carbide and the electrodes, and performing a second lift-off operation to fabricate an optically transparent ITO gate between the electrodes.

Claims

1. A method comprising the steps of: depositing a layer of silicon oxide onto a layer of silicon carbide; ion implanting the layer of silicon carbide; annealing the ion implanted layer of silicon carbide to produce defects within the layer of silicon carbide; performing photolithography using a mask layer on one or more regions of the layer of silicon carbide to define one or more regions for electrode deposition; removing the layer of silicon oxide from the layer of silicon carbide in the one or more regions for electrode deposition; forming one or more electrodes by depositing indium tin oxide (ITO) in each of the one or more regions for electrode deposition; performing a first lift-off operation to remove the mask layer surrounding the electrodes; depositing a passivation and gate silicon oxide layer on top of the layer of silicon carbide and the electrodes; and performing a second lift-off operation to fabricate an optically transparent ITO gate between the electrodes.

2. The method of claim 1, wherein the step of ion implanting is performed using .sup.12C.

3. The method of claim 1, wherein the step of ion implanting is performed using an energy level between a range of about 20 keV to about 50 keV.

4. The method of claim 1, wherein the step of annealing is performed at a temperature between a range of about 900 degrees Celsius to about 1000 degrees Celsius.

5. The method of claim 1, wherein the step of removing the layer of silicon oxide from the layer of silicon carbide is performed using a dilute H.sub.2O:HF etch.

6. The method of claim 1, wherein the step of depositing ITO is performed by RF sputtering at 200 W in argon.

7. The method of claim 1, wherein the step of performing a first lift-off operation is performed in acetone with ultrasonic agitation.

8. The method of claim 1, wherein the step of depositing a layer of silicon oxide onto a layer of silicon carbide is performed by atomic layer deposition.

9. The method of claim 1, wherein the layer of silicon carbide comprises 4H silicon carbide.

10. The method of claim 1, wherein the layer of silicon carbide comprises 6H silicon carbide.

11. A method comprising the steps of: depositing a layer of silicon oxide onto a layer of silicon carbide using atomic layer deposition; ion implanting the layer of silicon carbide using .sup.12C using an energy level between a range of about 20 keV to about 50 keV; annealing the ion implanted layer of silicon carbide at a temperature between a range of about 900 degrees Celsius to about 1000 degrees Celsius to produce defects within the layer of silicon carbide; performing photolithography on one or more regions of the layer of silicon carbide to define one or more regions for electrode deposition; removing the layer of silicon oxide from the layer of silicon carbide in the one or more regions for electrode deposition using a dilute H.sub.2O:HF etch; depositing indium tin oxide (ITO) in each of the one or more regions for electrode deposition; performing a first lift-off operation to remove the mask layer surrounding the electrodes; depositing a passivation and gate silicon oxide layer on top of the layer of silicon carbide and the electrodes; and performing a second lift-off operation to fabricate an optically transparent ITO gate between the electrodes.

12. The method of claim 11, wherein the step of depositing ITO is performed by RF sputtering at 200 W in argon.

13. The method of claim 1, wherein the step of performing a first lift-off operation is performed in acetone with ultrasonic agitation.

14. The method of claim 1, wherein the layer of silicon carbide comprises one of 4H silicon carbide and 6H silicon carbide.

15. A method comprising the steps of: depositing a layer of silicon oxide onto a layer of silicon carbide using atomic layer deposition, wherein the layer of silicon carbide comprises one of 4H silicon carbide and 6H silicon carbide; ion implanting the layer of silicon carbide using .sup.12C using an energy level between a range of about 20 keV to about 50 keV; annealing the ion implanted layer of silicon carbide at a temperature between a range of about 900 degrees Celsius to about 1000 degrees Celsius to produce defects within the layer of silicon carbide; performing photolithography on one or more regions of the layer of silicon carbide to define one or more regions for electrode deposition; removing the layer of silicon oxide from the layer of silicon carbide in the one or more regions for electrode deposition using a dilute H.sub.2O:HF etch; depositing indium tin oxide (ITO) in each of the one or more regions for electrode deposition using RF sputtering at 200 W in argon; performing a first lift-off operation to remove the mask layer surrounding the electrodes by using acetone with ultrasonic agitation; depositing a passivation and gate silicon oxide layer on top of the layer of silicon carbide and the electrodes; and performing a second lift-off operation to fabricate an optically transparent ITO gate between the electrodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A and 1B show diagrams illustrating lattice structures for 6H silicon carbide and 4H silicon carbide, respectively.

(2) FIG. 2 shows an energy level diagram in simplified form for the silicon vacancies in silicon carbide, illustrating the optical levels between the ground state and excited state and the associated situation with hyperfine splitting and the spin configurations.

(3) FIG. 3 shows a diagram illustrating energy levels for the full band structure of silicon carbide.

(4) FIGS. 4A-4F shows graphs illustrating optically detected magnetic resonance simulations of the identified spin 3/2 transitions with and without a nominal electric field.

(5) FIG. 5 shows a graph illustrating an ion implantation simulation of .sup.12C in silicon carbide for an implantation energy of 10 keV.

(6) FIG. 6 shows a graph illustrating an ion implantation simulation of .sup.12C in silicon carbide for an implantation energy of 20 keV.

(7) FIG. 7 shows a graph illustrating an ion implantation simulation of .sup.12C in silicon carbide for an implantation energy of 100 keV.

(8) FIG. 8 shows a diagram illustrating the process flow for fabrication of a device in accordance with the disclosed embodiments.

(9) FIG. 9 shows a top-down optical micrograph view of a representative device, in a ground-signal-ground configuration, fabricated in accordance with the embodiments of the method disclosed herein.

(10) FIG. 10 shows a scanning photoluminescence measurement of a device channel region for a 6H silicon carbide device implanted at 50 keV and a dose of 10.sup.13.

(11) FIG. 11 shows a photoluminescence image of the scanned region where the color of each data point is assigned based on the area-under-the-curve spanned by the markers in FIG. 12.

(12) FIG. 12 shows a graph illustrating the average spectra of the spectra encompassed by the regions shown in FIG. 11.

(13) FIG. 13 shows a photoluminescence image taken in the PL.sub.B region of the device shown in FIG. 9.

(14) FIG. 14 shows a graph illustrating the averaged spectra of the data points within the boxed regions shown in FIG. 13.

(15) FIG. 15 shows a photoluminescence image taken in the PL.sub.C region of the device shown in FIG. 9.

(16) FIG. 16 shows a graph illustrating the averaged spectra of the data points within the entire scanned region shown in FIG. 15.

(17) FIG. 17 shows a graph illustrating spectra of 6HSiC samples with varying implantation energies and doses normalized with respect to the 2.sup.nd TO Raman peak of 6HSiC.

(18) FIG. 18 shows a graph illustrating PL emission versus laser power for a 6HSiC sample implanted at 50 keV and a dose of 10.sup.13.

(19) FIG. 19 shows a flowchart of an embodiment of a method in accordance with the embodiments disclosed herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

(20) Reference in the specification to one embodiment or to an embodiment means that a particular element, feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment. The appearances of the phrases in one embodiment, in some embodiments, and in other embodiments in various places in the specification are not necessarily all referring to the same embodiment or the same set of embodiments.

(21) Some embodiments may be described using the expression coupled and connected along with their derivatives. For example, some embodiments may be described using the term coupled to indicate that two or more elements are in direct physical or electrical contact. The term coupled, however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.

(22) As used herein, the terms comprises, comprising, includes, including, has, having or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, or refers to an inclusive or and not to an exclusive or.

(23) Additionally, use of the a or an are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This detailed description should be read to include one or at least one and the singular also includes the plural unless it is obviously meant otherwise.

(24) The disclosed embodiments include a method for constructing silicon carbide defect qubits by ion implantation and high temperature annealing to form vacancies. Optically transparent indium tin oxide (ITO) electrodes are integrated in a layout suitable for microwave/RF excitation and optical input/output. The surface is passivated by an atomic layer deposited silicon oxide thin film to preserve the vacancy configurations. The devices are formed through 12C ion implantation and high-temperature annealing of 4H and 6H silicon carbide. The processing of the disclosed embodiments results in good contact being formed between ITO and SiC. The photoluminescence (PL) signature of silicon vacancies is readily detected both in the silicon oxide/silicon carbide (SiC) and ITO/SiC regions and is consistent with emission in SiC only regions. The density of vacancies is estimated and lower dose implant is found to result in a consistent reduction in the vacancy densities.

(25) A qubit is a two-level system that can be based on atoms, ions, quantum dots or even defects in crystals. The difference between these two-level systems and those based on classical objects are that they obey quantum mechanics and thus can permit quantum physics operation such as tunneling and entanglement on these two levels that effectively comprise quantum information states |0> and |1>. Using defects in crystals for qubits is advantageous in that they can be constructed using micro-nanofabrication techniques and can benefit from many of the advantages of high tech electronics such as scalability, low cost, large scale integration, compatibility with supporting components etc. There are a few types of solid state qubits being investigated worldwide and these include nitrogen vacancies in diamond, dopants in silicon, vacancies in silicon carbide and rare-earth ions in crystals. Regardless of the type of system used, the atom-like element must meet certain criteria to be used as a qubit.

(26) Vacancy defects in silicon-carbide are being pursued for use as qubits due to meeting several criteria specifically regarding spin states that can be controlled (i.e. rotated and flipped) with substantial quantum coherence time of these spin states via optical and microwave excitation, a kind of hybrid process that combines concepts from nuclear/electronic magnetic resonance and spintronic that can be implemented in the solid state with atom-like defects in a host crystal.

(27) FIGS. 1A and 1B show a general description of the atomic arrangements for 6HSiC and 4HSiC, respectively, illustrating the lattice arrangements and the location of vacancies. As shown in FIG. 1A, 6HSiC has ABCACBA periodicity. As shown in FIG. 1B, 4HSiC has ABCBA periodicity. The larger shaded regions in the lattice represent Si atoms, the smaller shaded regions in the lattice represent Carbon atoms, while the dashed regions in the lattice represent Si vacancies. It should be noted that due to non-ideality in the fabrication process other defects likely exist.

(28) FIG. 2 shows the energy level diagram in simplified form for silicon vacancies describing the optical levels between the ground state (GS) and excited state (ES) and the associated situation with hyperfine splitting and the spin configurations. FIG. 3 shows a diagram illustrating energy levels for the full band structure of SiC.

(29) According to recent density functional theory and experimental validation analysis, the physical effects behind a possible electric field tuning captured via an effective Stark-like effect of the qubit response is due largely to a combination of distortion of the atomic/ionic lattice as well as direct field-induced shifts of the wave-functions, where the latter is expected to be greater. Owing to the high polarizability with dielectric constant of 10 of SiC, the effects can be quite substantial and even stronger than that of diamond crystals.

(30) The embodiments of the methods disclosed herein address the need to passivate the surface of a silicon carbide defect qubit device to protect the vacancy configuration and the need to integrate contacts that are optically transparent so that the qubit can be excited and the optical emission can be detectable from the regions beneath the contacts. The embodiments of the disclosed methods further address implementation of a layout where microwave power can be inputted at frequencies commensurate with the driving frequencies for the energy level of the transitions of the qubit system. The embodiments of the disclosed methods also provide the ability to apply electric field in the c-axis direction (i.e. between contact and bottom of wafer) as well as in two-dimensions, i.e. in the channel region between contacts.

(31) The tunability of the qubits is enabled by utilizing the gates to immerse the qubits in an electric field and, by virtue of the Hamiltonian that is impacted, the qubit energy levels and spin transitions are modified. The tunability is also enabled by confining the qubit in an electrostatic potential created near the surface with a gate insulator sandwiched to further split the bands. For further control, the qubit can be embedded in the quantum well of a heterostructure formed between for example 4H SiC and Si or a crystalline insular with suitable energy barriers.

(32) In order to understand the operation of the qubits and to quantify the anticipated tuning of the qubit properties, a spin Hamiltonian model is employed and it is modified to include a term in the Hamiltonian corresponding to electric field. The objective is to recalculate the effect of electric field on the energy levels and resulting ODMR spectra, to search for possibility of tuning the ODMR or even discovery of potential for new transitions if significant perturbation of the energy levels is expected. The Hamiltonian considered without electric field is
H=g.sub.B{right arrow over (B)}.Math.{right arrow over (S)}+DS.sub.z.sup.2+H.sub.hf(Eq. 1)
where g is the electron factor, .sub.B is the Bohr magneton, {right arrow over (B)} is the magnetic field, 2D is the zero-magnetic field splitting parameter, {right arrow over (S)} is the vector of spin 3/2, and H.sub.hf is considering the hyperfine interaction between the next nearest neighbor (NNN) .sup.29Si nuclear spin and the silicon vacancy (defect) spin. Looking at the full lattice description and full band-structure it is possible that other factors contribute to the overall response of the material, but for the atom-like description and the regime of excitation, these elements are the primary factors of interest to the Hamiltonian in this analysis in describing the system and the elements that can be engineered. Further details on the model can be found in a publication by Carter et al., titled Spin Coherence and Echo Modulation of the Silicon Vacancy in 4HSiC at Room Temperature, Physical Review B, vol. 92, issue 16 (2015), the content of which is fully incorporated by reference herein.

(33) For the embodiments disclosed herein, an additional term is added to consider the effect of the electric field and to examine the impact on the energy levels as a function of magnetic field as well as the calculated optically detected magnetic resonance (ODMR) spectra. Based upon a recent publication by Falk et al., entitled Optical Polarization of Nuclear Spins in Silicon Carbide, Physical Review Letters, vol. 2, issue 24 (2014), the content of which is fully incorporated by reference herein, the modified Hamiltonian becomes with the H.sub.hf term expanded to include electric field matrices.
H=g.sub.B{right arrow over (B)}.Math.{right arrow over (S)}+DS.sub.Z.sup.2+(H.sub.hfE.sub.x(.sub.x.sup.2.sub.y.sup.2)+E.sub.y(.sub.x.sub.y+.sub.y.sub.x))(Eq. 2)
where E.sub.x and E.sub.y are field splitting parameters in the x and y directions, respectively, and .sub.x.sup.2 and .sub.y.sup.2 are the respective components of the appropriate spin vector for the Si vacancy.

(34) FIG. 3 shows calculated energy levels versus magnetic field with and without an additional electric field. Six transitions have been identified based on what is possible according to quantum mechanics for the spin 3/2 defects. FIGS. 4A-4F show graphs 100-150, respectively, of simulations of the ODMR spectra for these six transitions with and without an electric field. It is promising that significant sensitivity in the ODMR spectra is observable with nominal electric fields that would be readily resolvable in experiment.

(35) Starting materials are 4 4H and 6H purity semi-insulating silicon carbide, as well as 4 silicon control wafers for comparison. As an example, the wafers were diced into 19.5-x 19.5-mm squares. The size of the diced pieces may be varied based upon factors, such as, for example, ensuring compatibility with the thermal annealing furnace used in the process and making the source large enough to ensure that a device nears the center of the sample is minimally impacted by human wafer handling in the clean-room.

(36) After dicing, 8 nm of silicon oxide (SiOx) was deposited by atomic layer deposition (ALD) to serve as an implant and annealing cap. ALD is beneficial in that it is performed at a low temperature and does not disrupt the qubit properties. It should be noted that different thicknesses of SiOx may be used other than 8 nm. The thickness may be optimized for the specific electric field, passivation protection, and/or alternating materials that are used to form the heterostructure. ALD was performed based on standard recipes using water and (x) precursors at 200 C., although it should be noted that other temperatures may be used. As an example, one method that may be used herein for producing defects is by ion implantation with .sup.12C and subsequent high temperature annealing with 900-1000 C. temperatures. Typical doses range from 10.sup.11-10.sup.13 ions/cm.sup.2 and energies greater than 20 keV. As an example, implantation may span these ranges as well as at 10 keV to attempt to position the vacancies closer to the surface of the SiC in order to have vacancies in regions of highest electric field. Table 1 below shows examples of ion-implantation for various wafers.

(37) TABLE-US-00001 TABLE 1 Wafer # Species Dose (cm.sup.2) Energy (keV) Samples 1 .sup.12C 10.sup.11 200 4H SiC, 6H SiC, Si 2 .sup.12C 10.sup.12 200 4H SiC, 6H SiC, Si 3 .sup.12C 10.sup.13 200 4H SiC, 6H SiC, Si 4 .sup.12C 10.sup.11 50 4H SiC, 6H SiC, Si 5 .sup.12C 10.sup.12 50 4H SiC, 6H SiC, Si 6 .sup.12C 10.sup.13 50 4H SiC, 6H SiC, Si 7 .sup.12C 10.sup.11 20 4H SiC, 6H SiC, Si 8 .sup.12C 10.sup.12 20 4H SiC, 6H SiC, Si 9 .sup.12C 10.sup.13 20 4H SiC, 6H SiC, Si 10 .sup.12C 10.sup.11 10 4H SiC, 6H SiC, Si 11 .sup.12C 10.sup.12 10 4H SiC, 6H SiC, Si 12 .sup.12C 10.sup.13 10 4H SiC, 6H SiC, Si

(38) The ion implantations were simulated to estimate the doping and damage profiles through the depth of the material. The estimations are shown in graphs 200, 300, and 400 shown in FIGS. 5-7, respectively, as an example with dose of 10.sup.12 cm.sup.2 and energies of 10, 20, and 100 keV. According to the simulations and prior to annealing, the peak concentration of .sup.12C is at 20.5, 41.3, and 188 nm. Depth of ion implantation depends on the desired location of the qubit and if there is any internationally formed heterojunction of photonic crystal buried beneath. In the absence of that, it is desired for the qubit to be located very near the surface to ensure maximum coupling of the electric field. Also according to the simulations, at the above-mentioned dose, a high level of disorder is created. However, some of the disorder may be resolved by the annealing process. For each wafer samples of 4H and 6H, silicon control was mounted by taping the corners with polyimide tape avoiding contact with the center 10 mm of the samples. After implantation the samples were processed according the flow diagram 500 shown in FIG. 8.

(39) Thermal annealing was performed at 1000 C. for 30 minutes with a ULVAC MILA-3000 Mililamp annealer under low vacuum conditions. The thermal anneal is done to produce vacancies with a large percentage of vacancies that are suitable for use as qubits (i.e. silicon vacancies, and di-vacancies). However, other types of annealing, such as laser annealing, may be used. Following annealing, photolithography was performed to define lift-off regions for deposition of the electrodes. In one example, the mask contains field-effect device structures in a ground-signal-ground (G-S-G) configuration and with 150 m separation, as shown in the finished product in FIG. 9. The channel length is varied on the mask ranging from 200 m to 2 m. Photolithography is completed with a MA6 mask aligner. After photolithography, a dilute H.sub.2O:HF (1:50) etch is performed to etch the SiO.sub.x in the contact regions. After etch, deposition of ITO occurs by, for example, RF sputtering at 200 Watts in argon.

(40) After sputtering, a first lift-off operation is performed in acetone with ultrasonic agitation. As used herein, the term lift-off refers to the process in semiconductor wafer manufacturing of creating patterns on the wafer surface through an additive process, as opposed to the more familiar patterning techniques that involve subtractive processes, such as etching.

(41) The process then involves depositing a passivation and gate silicon oxide layer on top of the layer of silicon carbide and the electrodes, as well as performing a second lift-off operation to fabricate an optically transparent ITO gate between the electrodes. As used herein, the term optically transparent refers to transparency that permits both the excitation and emission of the desired wavelengths for the qubit operation. These two steps form a gate electrode directly above the qubit region in intimate contact with the SiOx passivation. A lift-off procedure may also be used following deposition of a transparent electrode, such as ITO.

(42) The output 600 is shown in FIG. 9, showing several ITO electrodes and noting three regions where photoluminescence (PL) measurements are taken, namely PL.sub.a, PL.sub.b, and PL.sub.c. The layout is in a ground-signal-ground (GSG) configuration spaced by 150 m suitable for direct microwave input via probes.

(43) As an example, scanning PL measurements were taken on both of the 4HSiC and 6HSiC samples at room temperature using an AIST-NT Confocal Raman/Atomic Force Microscopy (AFM) system with a laser excitation source of 785 nm, a Horiba iHR320 imaging spectrometer, and a Horiba Syncerity CCD camera thermoelectrically cooled to 50 C. with a Hamamatsu (S11510) near-IR image sensor. The samples measured include both non-implanted and .sup.12C implanted 4HSiC and 6HSiC with energies ranging from 20-50 keV and doses ranging from 10.sup.12-13. Measurements were also conducted on three different regions of the device to examine the effect of an ITO film on the excitation and transmission of SiC PL.

(44) FIG. 10 shows the scanning PL image 700 of the device channel region, PL.sub.a for a 6HSiC device implanted at 50 keV and a dose of 10.sup.13. FIG. 11 shows a PL image 800 of the scanned region where the color of each data point is assigned based on the area-under-the-curve (AUC) spanned by the green markers shown in graph 900 of FIG. 12. The region is a 30 m by 30 m square and the spectra were acquired every 500 nm with an acquisition time of 100 ms using a 30 mW excitation at 785 nm.

(45) The blue and red spectra shown in FIG. 12 are the average spectra of the spectra encompassed by the blue and red regions, respectively, shown in image 800 of FIG. 11. The blue region corresponds to 6HSiC/SiO.sub.x within the device channel and the red region corresponds to 6HSiC/ITO/SiO.sub.x. The broad PL peak in FIG. 11 spanning 825-1050 nm is suggestive of silicon vacancy defects in 6HSiC. As these measurements were completed at room temperature, the PL shows a broad phonon sideband. In order to lessen the effect of electron-phonon coupling and to observe the sharp zero phonon line transitions of the defects, the device must be cooled. Additionally, small peaks corresponding to the tangential and longitudinal optical modes (TO, LO, respectively) of 6HSiC are present (830-850 nm). The suggests that ITO has minimal impact on the transmission of the PL as confirmed by similar PL intensities and presence of 6HSiC Raman peaks in the 6HSiC/SiO.sub.x and 6HSiC/ITO/SiOx regions.

(46) FIG. 13 shows a scanning PL image 1000 of the ITO electrode region, PL.sub.B, for a 6HSiC device implanted at 50 keV and a dose of 10.sup.13. FIG. 13 shows a PL image of the scanned region where the color of each data point is assigned based on the area-under-the-curve (AUC) spanned by the green markers of graph 1100 shown in FIG. 14. The region is a 30 m by 20 m and the spectra were acquired every 500 nm with an acquisition time of 100 ms using a 30 mW excitation at 785 nm. The blue and red spectra shown in graph 1100 are the average spectra of the spectra encompassed by the blue and red regions, respectively, of image 1000 shown in FIG. 13. Both the blue and the red region correspond to 6HSiC/ITO/SiO.sub.x. The spectra shown in FIG. 14 correspond closely with the spectra shown in FIG. 12, as the ITO film appears to have minimal impact on observing the PL of 6HSiC.

(47) FIGS. 15 and 16 show the scanning PL measurement of the 6HSiC/SiO.sub.x region away from the device, PL.sub.C, implanted at 50 keV and a dose of 10.sup.13. FIG. 15 shows a PL image 1200 of the scanned region where the color of each data point is assigned based on the maximum peak intensity of the collected spectra. The region is a 20 m by 20 m and the spectra were acquired every 500 nm with an acquisition time of 100 ms using a 30 mW excitation at 785 nm. FIG. 16 shows a graph 1300 illustrating the average spectrum of the entire region. Comparing the spectra of FIGS. 12, 14, and 16 demonstrates that the ITO and SiO.sub.x films have minimal impact on observing the PL of 6HSiC and that the PL is nearly uniform between different regions of the sample.

(48) To confirm the effect of energy and dose in introducing defects in 6HSiC, the PL measurements were conducted on three samples. These samples included unprocessed 6HSiC, 6HSiC implanted at 20 keV with dose of 10.sup.12, and 6HSiC implanted at 50 keV with dose of 10.sup.13. The samples were measured using a 785 nm excitation at 100 mW. The average spectra were acquired with an acquisition time of is and 10 accumulations, and were normalized with respect to the 2.sup.nd TO peak of 6HSiC. FIG. 17 shows a graph 1400 illustrating the average spectra of these measurements. With increasing dose and energy, the PL intensity increases indicative of increased number of defects in 6HSiC.

(49) To estimate the quantity of photon emitting defects within the excitation volume, the PL of an implanted 6HSiC sample (Energy: 50 keV; Dose: 10.sup.13) was measured at a series of laser powers. FIG. 18 shows a graph 1500 illustrating the counts per second (cps) of the PL with respect to laser power from 0 to 100 mW. The data was fit to the equation f(x)=a/(1+(b/x)) where a corresponds to the cps when all emitters within the volume are saturated and b corresponds the laser power to achieve half of the saturated emission. Using an estimated 10.sup.4 cps for a single emitter, the estimated emitters within the excitation volume is 300. By varying the dose and energy of implantation, it may be possible to the decrease the number of emitting defects to achieve devices with single defects.

(50) FIG. 19 shows a flowchart of an embodiment of a method 1600 in accordance with the embodiments disclosed herein. While FIG. 19 shows one embodiment of method 100 to include steps 110-180, other embodiments of method 1600 may contain fewer or more steps. Further, while in some embodiments the steps of method 1600 may be performed as shown in FIG. 19, in other embodiments the steps may be performed in a different order, or certain steps may occur simultaneously with one or more other steps.

(51) Method 1600 may begin with step 1610, which involves depositing a layer of silicon oxide onto a layer of silicon carbide, such as 4H or 6H silicon carbide. Step 1620 involves ion implanting the layer of silicon carbide. As an example, step 1620 is performed using .sup.12C. In some embodiments, step 1620 is performed using an energy level between a range of about 20 keV to about 50 keV. Step 1630 involves annealing the ion implanted layer of silicon carbide to produce defects within the layer of silicon carbide. In some embodiments, step 1630 is performed at a temperature between a range of about 900 degrees Celsius to about 1000 degrees Celsius.

(52) Step 1640 involves performing photolithography using a mask layer on regions of the layer of silicon carbide to define regions for electrode deposition. Step 1650 involves removing the layer of silicon oxide from the layer of silicon carbide in the one or more regions for electrode deposition. In some embodiments, step 1650 is performed using a dilute H.sub.2O:HF etch. Step 1660 involves forming one or more electrodes by depositing indium tin oxide (ITO) in each of the regions for electrode deposition. As an example, step 1660 is performed by RF sputtering at 200 W in argon.

(53) Step 1670 involves performing a first lift-off operation to remove the mask layer surrounding the electrodes. In some embodiments, step 1670 is performed in acetone with ultrasonic agitation. Step 1680 involves depositing a passivation and gate silicon oxide layer on top of the layer of silicon carbide and the electrodes. In some embodiments, step 1680 is performed by atomic layer deposition. Step 1690 involves performing a second lift-off operation to fabricate an optically transparent ITO gate between the electrodes.

(54) Many modifications and variations of the embodiments disclosed herein are possible in light of the above description. Within the scope of the appended claims, the disclosed embodiments may be practiced otherwise than as specifically described. Further, the scope of the claims is not limited to the implementations and embodiments disclosed herein, but extends to other implementations and embodiments as may be contemplated by those having ordinary skill in the art.