HIGH-EFFICIENCY 1,000NM INFRARED LIGHT EMITTING DIODE, AND MANUFACTURING METHOD THEREOF

Abstract

The present invention relates to an infrared light emitting diode and a manufacturing method thereof, and more specifically, to a 1,000 nm infrared light emitting diode with improved light emitting efficiency through compensation of strain, and a manufacturing method thereof.

Claims

1. An infrared light emitting diode comprising: an In.sub.xGa.sub.1-xAs quantum well layer (0.13x0.15) having compressive strain; a GaAs.sub.1-yP.sub.y quantum barrier layer (0.07y0.11) having tensile strain; and an active layer including a GaInP strain compensation barrier having compressive strain lower than that of the quantum barrier layer, and a GaAs buffer layer.

2. The infrared light emitting diode according to claim 1, wherein the InGaAs quantum well layer and the GaAsP quantum barrier layer are alternately stacked, and the GaInP strain compensation barrier is positioned between the alternately stacked InGaAs quantum well layer and GaAsP quantum barrier layer.

3. The infrared light emitting diode according to claim 1, wherein the GaAs buffer layer is stacked between the InGaAs quantum well layer and GaInP strain compensation barrier and between the GaAsP quantum barrier layer and the GaInP strain correction layer.

4. The infrared light emitting diode according to claim 1, wherein the InGaAs quantum well layer and the GaAsP quantum barrier layer are alternately stacked, and a GaAs buffer layer, a GaInP strain compensation barrier and a GaAs buffer layer are grown and stacked between the InGaAs quantum well layer and the GaAsP quantum barrier layer.

5. The infrared light emitting diode according to claim 1, wherein the infrared light emitting diode is an infrared light emitting diode having a 1,000 nm center wavelength.

6. The infrared light emitting diode according to claim 5, comprising: a GaAs substrate; a first type AlGaAs lower confinement layer grown on the substrate; an active layer grown on the first type AlGaAs lower confinement layer; a second type AlGaAs upper confinement layer grown on the active layer; a p-type window layer formed on the upper confinement layer; and an upper electrode and a lower electrode respectively contacting with a top surface and a bottom surface of the p-type window layer and the GaAs substrate.

7. The infrared light emitting diode according to claim 1, wherein the quantum well layer is In.sub.0.15Ga.sub.0.85As, and the quantum barrier layer is GaAs.sub.0.91P.sub.0.09.

8. The infrared light emitting diode according to claim 1, wherein the GaInP strain compensation barrier is zero strain GaInP.

9. The infrared light emitting diode according to claim 1, wherein the GaInP strain compensation barrier is Ga.sub.zIn.sub.1-zP, wherein 0.50<z<0.59.

10. The infrared light emitting diode according to claim 1, wherein GaAs is a un-doped GaAs layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a view schematically showing the structure of a 940 nm infrared light emitting diode having an active layer in which an In.sub.xGa.sub.1-xAs quantum well layer and a GaAs quantum barrier layer manufactured by a MOCVD system in a conventional technique are alternately stacked.

[0040] FIG. 2 is a view schematically showing the structure of a 1,000 nm infrared light emitting diode having an active layer configured of an In.sub.xGa.sub.1-xAs quantum well layer and a GaAsP quantum barrier layer alternately stacked and manufactured by a MOCVD system, and a GaAs buffer layer, an In.sub.xGa.sub.1-xP strain compensation barrier and a GaAs buffer layer stacked there between according to the present invention.

[0041] FIG. 3 is a view showing the structure of various active layers that can be used in the light emitting diode of FIG. 2. (a) InGaAs/GaAs, (b) InGaAs/GaAsP, (c) InGaAs/GaAs/GaInP/GaAs/GaAsP

[0042] FIG. 4 is a view showing the XRD characteristics according to composition of (a) an In.sub.0.15Ga.sub.0.85As layer configuring a quantum well layer and (b) a GaAs.sub.1-yP.sub.y layer configuring a quantum barrier layer.

[0043] FIG. 5 is a view showing the PL characteristic according to composition of GaAsP of an InGaAs/GaAs active layer and an InGaAs/GaAs.sub.1-yP.sub.y active layer of the prior art.

[0044] FIG. 6 is a view showing the PL characteristic according to composition of GaInP in an InGaAs/GaAs/Ga.sub.zIn.sub.1-zP/GaAs/GaAsP active layer.

[0045] FIG. 7 is a view showing the optical characteristics of 1,000 nm infrared light emitting diodes having a conventional InGaAs/GaAs active layer, a compared InGaAs/GaAsP active layer, and an InGaAs/GaAs/Ga.sub.zIn.sub.1-zP/GaAs/GaAsP active layer according to the present invention.

DESCRIPTION OF SYMBOLS

[0046] 10: Light emitting diode [0047] 11: Upper electrode [0048] 12: Window layer [0049] 13: P-type confinement layer [0050] 17: n-type confinement layer [0051] 18: Substrate [0052] 19: Lower electrode [0053] 20: Active layer [0054] 21: Quantum well [0055] 22: Quantum barrier [0056] 23: Strain correction layer [0057] 24: Buffer layer

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0058] Hereinafter, the present invention will be described in detail through the embodiments.

Embodiment 1

[0059] FIG. 2 is a view schematically showing the structure of a 1,000 nm infrared light emitting diode having an active layer configured of an InGaAs quantum well layer and a GaAsP quantum barrier layer alternately stacked by a MOCVD system, and a GaAs buffer layer, an InGaP strain compensation barrier and a GaAs buffer layer stacked between the alternately stacked quantum well layer and quantum barrier layer.

[0060] As shown in FIG. 2, a 1,000 nm infrared light emitting diode 10 has a lower n-type GaAs substrate 18, an n-type lower confinement layer 17 configured of Al.sub.0.3Ga.sub.0.7As grown on the n-type GaAs substrate 18, an active layer 20 grown on the n-type lower confinement layer 17, a p-type upper confinement layer 13 grown on the active layer 20 as Al.sub.0.3Ga.sub.0.7As, and a window layer 12 configured of Al.sub.0.2Ga.sub.0.8As grown on the p-type upper confinement layer 13 at a thickness of 5 m to obtain a current diffusion effect and an emission cone zone expansion effect of the infrared light emitting diode. A lower electrode 19 configured of AuGeNi is formed on the bottom of the n-type GaAs substrate 18, and an upper electrode 11 configured of AuZn is formed on the top of the window layer 12.

[0061] In the active layer 20, an In.sub.0.15Ga.sub.0.85As quantum well 21 and a GaAs.sub.0.91P.sub.0.09 quantum barrier 22 are alternately and repeatedly grown five times, and a GaAs buffer layer 24, a Ga.sub.0.53In.sub.0.47P strain compensation barrier 23, and a GaAs buffer layer 24 are grown between the quantum well 21 and the quantum barrier 22. The Ga.sub.0.53In.sub.0.47P strain compensation barrier 23 has tensile strain of 1,000 ppm. Photoluminescence (PL) intensity of a 1,000 nm center wavelength diode 10 having the layer structure of FIG. 2 is measured. A result of the measurement is shown in FIG. 7. (InGaAs/GaInP/GaAsP0.09MQWs)

Comparative Embodiment 1

[0062] A light emitting diode having a structure the same as that of the diode 10 of embodiment 1, except that the In.sub.0.15Ga.sub.0.85As quantum well layer and the GaAs quantum barrier layer are alternately stacked five times as shown in FIG. 3(a), is manufactured, and photoluminescence (PL) intensity is measured. A result of the measurement is shown in FIG. 5(a).

Comparative Embodiment 2-1

[0063] A light emitting diode having a structure the same as that of the diode 10 of embodiment 1, except that the In.sub.0.15Ga.sub.0.85As quantum well layer and the GaAs.sub.0.97P.sub.0.03 quantum barrier layer are alternately stacked five times as shown in FIG. 3(b), is manufactured, and photoluminescence (PL) intensity is measured. A result of the measurement is shown in FIG. 5(b).

Comparative Embodiment 2-1

[0064] A light emitting diode having a structure the same as that of the diode 10 of embodiment 1, except that the In.sub.0.15Ga.sub.0.85As quantum well layer and the GaAs.sub.0.94P.sub.0.06 quantum barrier layer are alternately stacked five times as shown in FIG. 3(b), is manufactured, and photoluminescence (PL) intensity is measured. A result of the measurement is shown in FIG. 5(b).

Comparative Embodiment 2-3

[0065] A light emitting diode having a structure the same as that of the diode 10 of embodiment 1, except that the In.sub.0.15Ga.sub.0.85As quantum well layer and the GaAs.sub.0.91P.sub.0.09 quantum barrier layer are alternately stacked five times as shown in FIG. 3(b), is manufactured, and photoluminescence (PL) intensity is measured. A result of the measurement is shown in FIG. 5(b).

Embodiment 2

[0066] In embodiment 1, the active layer 20 has an In.sub.0.15Ga.sub.0.85As quantum well 21 and a GaAs.sub.0.91P.sub.0.09 quantum barrier 22 alternately and repeatedly grown five times, and a GaAs buffer layer 24, a Ga.sub.0.50In.sub.0.50P strain compensation barrier 23, and a GaAs buffer layer 24 are grown between the quantum well 21 and the quantum barrier 22. Here, the Ga.sub.0.50In.sub.0.50P strain compensation barrier does not have tensile strain. Photoluminescence (PL) intensity of a 1,000 nm center wavelength diode 10 having the layer structure of FIG. 2 is measured. A result of the measurement is shown in FIG. 6.

Comparative Embodiment 3

[0067] In embodiment 1, the active layer 20 has an In.sub.0.15Ga.sub.0.85As quantum well 21 and a GaAs.sub.0.91P.sub.0.09 quantum barrier 22 alternately and repeatedly grown five times, and a GaAs buffer layer 24, a Ga.sub.0.47In.sub.0.53P strain compensation barrier 23, and a GaAs buffer layer 24 are grown between the quantum well 21 and the quantum barrier 22. Here, the Ga.sub.0.47In.sub.0.53P strain compensation barrier has tensile strain of 1,000 ppm. Photoluminescence (PL) intensity of a 1,000 nm center wavelength diode 10 having the layer structure of FIG. 2 is measured. A result of the measurement is shown in FIG. 6.

[0068] Discussions

[0069] FIG. 4 is a view showing the XRD characteristics of (a) an In.sub.0.15Ga.sub.0.85As quantum well layer and (b) a GaAs.sub.1-yP.sub.y strain compensation barrier. All the layers are grown on the GaAs substrate as a single layer and scanned under the condition of omega-2theta. The layers have characteristics of compressive strain when they move in a direction of arcsec lower than that of the GaAs substrate (32.9 arcsec) and have characteristics of tensile strain when they move in a direction of arcsec higher than that of the GaAs substrate.

[0070] As shown in FIG. 4, in the case of In.sub.0.15Ga.sub.0.85As used as a light emission quantum well of a 1,000 nm infrared light emitting diode, it has extremely high compressive strain (+11,000 ppm) at 32.05 arcsec compared with that of GaAs (32.9 arcsec), and GaAs.sub.1-yP.sub.y has tensile strain. GaAs.sub.1-yP.sub.y shows a tendency of increasing the degree of tensile strain as the y value increases, and it is known that it has tensile strain of GaAs.sub.0.97P.sub.0.03 (1,500 ppm), GaAs.sub.0.94P.sub.0.05 (3,000 ppm), and GaAs.sub.0.91P.sub.0.09 (4,500 ppm).

[0071] As shown in comparative embodiment 1, when a quantum well layer having high compressive strain is alternately stacked together with a GaAs quantum barrier layer without having compressive strain, the 1,000 nm center wavelength light emitting diode does not improve the compressive strain caused by the quantum well layer and has a low PL intensity of 4 units as shown in FIG. 5(a).

[0072] As shown in comparative embodiments 2-1, 2-2 and 2-3, when a quantum well layer having high compressive strain is alternately stacked together with a GaAs.sub.1-yP.sub.y quantum barrier layer having tensile strain, the 1,000 nm center wavelength light emitting diode improves the compressive strain caused by the quantum well layer by the quantum barrier layer having tensile strain and has an improved PL intensity of 5 to 6 units as shown in FIG. 5(b). A quantum barrier layer having high tensile strain shows a relatively high PL intensity compared with a quantum barrier layer having low tensile strain.

[0073] As shown in embodiment 1, embodiment 2 and comparative embodiment 3, when a strain compensation barrier of Ga.sub.zIn.sub.1-zP and a buffer layer of GaAs are positioned between the quantum well layer and the quantum barrier layer in the form of a composite layer of GaAs/Ga.sub.zIn.sub.1-zP/GaAs while the In.sub.0.15Ga.sub.0.85As quantum well layer and the GaAs.sub.0.91P.sub.0.09 a quantum barrier layer are alternately stacked, the photoluminescence (PL) characteristic is affected by the characteristic of the strain compensation barrier of Ga.sub.zIn.sub.1-zP.

[0074] As shown in comparative embodiment 3, when the Ga.sub.zIn.sub.1-zP strain compensation barrier has compressive strain (z=0.53) in the form of Ga.sub.0.53In.sub.0.47P, the PL intensity is 6.2 units, which is slightly lower than or almost the same as that of a case where GaAs of the GaAs/Ga.sub.zIn.sub.1-zP/GaAs layer does not exist between the quantum well layer and the quantum barrier layer (comparative embodiment 2-3).

[0075] Contrarily, as shown in embodiment 1, when the Ga.sub.zIn.sub.1-zP strain compensation barrier has tensile strain (z=0.53) in the form of Ga.sub.0.47In.sub.0.53P, the PL intensity greatly increases to 7.9 units.

[0076] In addition, as shown in embodiment 2, even when the Ga.sub.zIn.sub.1-zP strain compensation barrier has zero strain (x=0.5) in the form of Ga.sub.0.50In.sub.0.50P, the PL intensity greatly increases to 7.2 units. Such a result shows that the tensile strain characteristic of the Ga.sub.zIn.sub.1-zP strain compensation barrier has adjusted strain non-uniform condition (compensation strain condition: +6, 500 ppm) generated by the In.sub.0.15Ga.sub.0.85As/GaAs.sub.0.91P.sub.0.09 MQW in a more balanced way, and contrarily, it is shown that the compressive strain characteristic of the Ga.sub.zIn.sub.1-zP strain compensation barrier greatly or negatively affects the non-uniform condition. In addition, a greatly improved characteristic is confirmed even when the Ga.sub.zIn.sub.1-zP strain condition is zero strain, and such a result shows that non-uniformity of the In.sub.0.15Ga.sub.0.85As/GaAs.sub.0.991P.sub.0.09 MQW layer is improved by the GaAs buffer layer essentially inserted in the boundary surface when the Ga.sub.zIn.sub.1-zP strain compensation barrier is applied.

[0077] According to the present invention, a problem according to the strain of the quantum well layer of an infrared light emitting diode of 1,000 nm center wavelength, which uses a GaAs substrate having a high lattice matching rate and an effect of high cost reduction (economical efficiency), is solved, and thus an infrared light emitting diode with improved light emitting efficiency is provided.

[0078] In the present invention, as the active layer of the 1,000 nm infrared light emitting diode with compensated strain improves a non-uniform strain condition of the InGaAs quantum well layer having compressive strain and the GaAsP quantum barrier having tensile strain through the GaInP strain compensation barrier and the buffer layers formed on the top and bottom surfaces of the GaInP strain correction layer, a high-efficiency 1,000 nm infrared light emitting diode having efficiency relatively increased by 20% is provided.

[0079] According to the present invention, the defect caused by compressive strain of the quantum well layer having large compressive strain with respect to the substrate can be solved.