Substituted aluminum nitride for improved acoustic wave filters

Abstract

An acoustic wave resonator comprises a piezoelectric material formed of aluminum nitride (AlN) doped with calcium (Ca) to enhance performance of the acoustic wave resonator.

Claims

1. An acoustic wave resonator comprising a piezoelectric material formed of aluminum nitride doped with calcium to enhance performance of the acoustic wave resonator, wherein the calcium is charge balanced with at least one of silicon and germanium and the piezoelectric material has a chemical formula of one of
Al.sub.1−2xCa.sub.xSi.sub.xN (0<x<1); or
Al.sub.1−2xCa.sub.xGe.sub.xN (0<x<1).

2. An acoustic wave filter including the acoustic wave resonator of claim 1.

3. The acoustic wave filter of claim 2 wherein the acoustic wave resonator is a bulk acoustic wave resonator.

4. The acoustic wave filter of claim 3 wherein the bulk acoustic wave resonator is one of a film bulk acoustic wave resonator, a Lamb wave resonator, or a surface mounted resonator.

5. The acoustic wave filter of claim 3 wherein the acoustic wave filter is a radio frequency filter.

6. An electronics module including the acoustic wave filter of claim 5.

7. An electronic device including the electronics module of claim 6.

8. The acoustic wave resonator of claim 1 wherein the piezoelectric material has a Wurtzite crystal structure.

9. A method of forming an acoustic wave resonator comprising: forming a piezoelectric film formed of aluminum nitride doped with calcium, wherein the calcium is charge balanced with at least one of silicon and germanium and the piezoelectric material has a chemical formula of one of
Al.sub.1−2xCa.sub.xSi.sub.xN (0<x<1); or
Al.sub.1−2xCa.sub.xGe.sub.xN (0<x<1); and depositing electrodes on the piezoelectric film to form the acoustic wave resonator.

10. The method of claim 9 wherein depositing the electrodes on the piezoelectric film in includes depositing a first electrode on a top surface of the piezoelectric film and depositing a second electrode on a bottom surface of the piezoelectric film.

11. The method of claim 10 wherein the acoustic wave resonator is a film bulk acoustic wave resonator and the method further comprises defining a cavity below the bottom surface of the piezoelectric film.

12. The method of claim 10 wherein the acoustic wave resonator is a Lamb wave resonator and depositing the first electrode on the top surface of the piezoelectric film comprises depositing interdigital transducer electrodes on the top surface of the piezoelectric film.

13. The method of claim 10 wherein the acoustic wave resonator is a solidly mounted resonator and the method further comprises forming the piezoelectric film on a top surface of a Bragg reflector.

14. An acoustic wave resonator including a film of piezoelectric material and an electrode disposed on the film of piezoelectric material, the film of piezoelectric material comprising: AlN doped with cations of one or more elements selected from the group consisting of: a) one of Sb, or Nb; b) Cr in combination with one or more of B, Sc, Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, or Yb; c) one of Nb and Ta in combination with one of Li, Ca, Ni, or Co; d) Ca in combination with one of Si or Ge; e) Mg in combination with one of Si or Ge; or f) one or more of Co, Sb, Ta, Nb, Si, or Ge in combination with one or more of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, or Yb; the cations at least partially substituting for Al in a crystal structure of the piezoelectric material.

15. The acoustic wave resonator of claim 14 wherein the piezoelectric material has a Wurtzite crystal structure.

16. The acoustic wave resonator of claim 14 configured as a solidly mounted resonator.

17. The acoustic wave resonator of claim 14 configured as a film bulk acoustic resonator.

18. A filter including the acoustic wave resonator of claim 14.

19. The filter of claim 18 having a passband in the radio frequency band.

20. An electronic device module including the filter of claim 18.

21. An electronic device including the electronic device module of claim 20.

22. The electronic device of claim 21 wherein the electronic device module is a radio frequency electronic device module.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a chart of impedance vs. frequency for an example of an acoustic wave filter;

(2) FIG. 2 is a chart illustrating the dielectric polarizabilities of various trivalent cations vs. crystal radius;

(3) FIG. 3 is a table of selected material parameters of various electromechanical materials;

(4) FIG. 4 illustrates the Wurtzite crystallographic structure;

(5) FIG. 5A is a table of selected material parameters for various III-V Wurtzite nitrides and II-VI Wurtzite oxides;

(6) FIG. 5B is a table of selected material parameters of AlN, GaN, and InN;

(7) FIG. 6A is a chart of lattice constant vs. x in Al.sub.xGa.sub.1−xN;

(8) FIG. 6B is a chart of energy gap vs. x in Al.sub.xGa.sub.1−xN;

(9) FIG. 7A is a chart of elastic constant vs. Phillips Ionicity for selected compounds;

(10) FIG. 7B is a chart of sound velocity vs. Phillips Ionicity for selected compounds;

(11) FIG. 8A is a chart illustrating the change in crystallographic structure vs. c/a ratio in Sc.sub.0.5Al.sub.0.5N;

(12) FIG. 8B is another chart illustrating the change in crystallographic structure vs c/a ratio in Sc.sub.0.5Al.sub.0.5N;

(13) FIG. 8C is a table of select material properties of AlN and Al.sub.0.88Sc.sub.0.12N.

(14) FIG. 8D is a table of select material properties of AlN and AlN doped with various concentrations of Sc.

(15) FIG. 8E is a chart of k.sup.2 and Q-factor for AlN doped with various concentrations of Sc;

(16) FIG. 8F is a chart of ε.sub.r and tan δ for AlN doped with various concentrations of Sc;

(17) FIG. 8G is a chart of FOM for AlN doped with various concentrations of Sc;

(18) FIG. 8H is a chart of TCF for AlN doped with various concentrations of Sc;

(19) FIG. 9A is a chart of ε.sub.r for AlN doped with various concentrations of Y;

(20) FIG. 9B is a chart of e.sub.33 and e.sub.31 for AlN doped with various concentrations of Y;

(21) FIG. 9C is a chart of d.sub.33, and d.sub.31 for AlN doped with various concentrations of Y;

(22) FIG. 10A is a chart of e.sub.33 vs. dopant concentration for AlN doped with Sc, and with coupled substitution of Mg and Zr, Mg and Ti, and Mg and Hf for Al;

(23) FIG. 10B is a chart of c.sub.33 vs. dopant concentration for AlN doped with Sc, and with coupled substitution of Mg and Zr, Mg and Ti, and Mg and Hf for Al;

(24) FIG. 10C is a table of selected material properties of AlN, (Mg.sub.0.5Zr.sub.0.5).sub.0.13Al.sub.0.87N and (Mg.sub.0.5Hf.sub.0.5).sub.0.13Al.sub.0.87N;

(25) FIG. 11A is a chart of c.sub.33 vs. boron concentration in boron-doped AlN;

(26) FIG. 11B is a chart of e.sub.33 vs. boron concentration in boron-doped AlN;

(27) FIG. 11C is a chart of crystal lattice parameter c vs. boron concentration in boron-doped AlN;

(28) FIG. 11D is a chart of k.sup.2 vs. boron concentration in boron-doped AlN;

(29) FIG. 11E is a chart of crystal unit cell volume vs. boron concentration in boron-doped AlN;

(30) FIG. 11F is a chart of crystal lattice parameters c and a vs. boron concentration in boron-doped AlN;

(31) FIG. 12A is a chart of material resistivity vs. temperature for Al.sub.0.93Cr.sub.0.07N and Al.sub.0.91Mn.sub.0.09N;

(32) FIG. 12B is a chart of lattice constant vs. Cr concentration in Cr-doped AlN;

(33) FIG. 12C is a chart of effective d.sub.33 vs. Cr concentration in Cr-doped AlN;

(34) FIG. 13 is a chart of k.sup.2, v.sub.s, and dielectric constant vs. Ti concentration in Ti-doped AlN;

(35) FIG. 14A is a chart of acoustic velocity and dielectric constant vs. V content in V-doped AlN;

(36) FIG. 14B is a chart of acoustic velocity and dielectric constant vs. Ta content in Ta-doped AlN;

(37) FIG. 14C is a chart of lattice constant vs. Ta content in Ta-doped AlN;

(38) FIG. 14D is a chart of piezoelectric coefficient d.sub.33 vs. Ta content in Ta-doped AlN;

(39) FIG. 15 illustrates conflicting tradeoffs in materials properties for different dopants in AlN;

(40) FIG. 16 is a table indicating the expected effect of various dopants on selected material properties of doped AlN;

(41) FIG. 17 is a cross-sectional view of an example of a solidly mounted resonator (SMR) BAW;

(42) FIG. 18 is a cross-sectional view of an example of an FBAR BAW; and

(43) FIG. 19 is a schematic view of a filter than may include SMR BAW and/or FBAR BAW devices;

(44) FIG. 20 is a block diagram of a front-end module in which the filter of FIG. 19 may be implemented; and

(45) FIG. 21 is a block diagram of a wireless device in which the filter of FIG. 19 may be implemented.

DETAILED DESCRIPTION

(46) Analysis of crystal chemical systematics from previous work has provided insights into how specific chemical substituents for aluminum (Al) in aluminum nitride (AlN) affect various properties of interest of the material. Disclosed herein are new chemical substituent combinations for AlN that may be used to form a piezoelectric material for use in acoustic wave filters such as Bulk Acoustic Wave (BAW) and Film Bulk Acoustic Resonator (FBAR) filters. Advantages of the solutions disclosed herein over previous solutions are that multiple material properties may be simultaneously optimized (for example, electromechanical coupling and sound velocity). Based on the knowledge of crystal chemistry and previous work, there appears to be a series of mutually exclusive property combinations resulting from doping for Al in AlN-based piezoelectric materials. For example, substitutions which form a more ionic bond with nitrogen than aluminum (such as scandium) will improve the coupling and dielectric constant whereas substitutions which form a more covalent bond with nitrogen than aluminum (such as boron) will improve the sound velocity and decrease viscoelastic losses. Disclosed herein are AlN-based piezoelectric materials which may exhibit improvements in multiple properties or which may exhibit extreme enhancements for specific individual properties (e.g. dielectric constant).

(47) The most frequently cited additive to AlN is scandium (Sc). Scandium is more electropositive than Al. Increased ionicity of Sc.sup.3+ relative to Al.sup.3+ increases the piezoelectric coupling of Sc-doped AlN as compared to un-doped AlN. Sc.sup.3+ is also larger than Al.sup.3+. Distortion of the crystal lattice of AlN due to the presence of Sc.sup.3+ substituted for Al.sup.3+ increases the piezoelectric coefficient of Sc-doped AlN as compared to un-doped AlN. The loss of covalency due to the presence of Sc.sup.3+ substituted for Al.sup.3+ however, increases viscoelastic losses.

(48) Y, Yb and other small lanthanides are larger ions than Sc.sup.3+ and are more electropositive than Sc. Substitution of Al.sup.3+ in AlN with ions of these elements may enhance both piezoelectric effect and viscoelastic losses. Heavier polarizable atoms such as Yb.sup.3+ should improve the dielectric constant of the doped AlN more than lighter atoms such as Sc.sup.3+ and Y.sup.3+. Multiple isovalent substitutions (AlN:B, Sc or AlN:B, Yb) may also be used.

(49) In contrast with Sc, Y, and Yb, boron (B) forms a much smaller ion than Al and is less electropositive than Al. Boron would form a more covalent bond with N than Al. Piezoelectric coupling may be expected to decrease slightly with B substitution for Al in AlN, but viscoelastic losses should decrease as well. The increased covalency of B—N bonds relative to Al—N bonds should increase the bulk modulus of B-doped AlN as compared to un-doped AlN. Light B atoms substituting for Al should also decrease the density of B-doped AlN as compared to un-doped AlN. Both effects should combine to give greater acoustic velocity (v=(K/ρ).sup.1/2, K=Bulk Modulus of Material; ρ=Density).

(50) Dopants for Al in AlN which enhance Q, elastic modulus, and sound velocity of the material appear to work against improved coupling coefficients and higher dielectric constants. This is represented schematically in FIG. 15. Simultaneous additions of different dopants and/or doping AlN to facilitate 3d electron interactions or to form ordered vacant lattice sites may provide the benefits associated with both highly electropositive and weakly electropositive dopants.

(51) In transition metals, the d-electron manifold greatly complicates bonding. Ions may have preference for octahedral or tetrahedral coordination depending on d electron count. For example, Cr.sup.3+ has extremely strong preference for octahedral coordination. If forced into a tetrahedral site, this may create strong lattice distortions enhancing piezoelectricity (even though the Cr.sup.3+ ion is not as electropositive as Sc). Coupled substitution of B and Cr may produce lattice distortions enhancing piezoelectricity without viscoelastic losses. Other ions such as V.sup.3+, Mn.sup.3+, and Co.sup.3+ can be useful as dopants to improve the properties of AlN. These ions can adjust to different oxidation states with Co.sup.3+ having several spin states per oxidation state and can thus exhibit multiple different ionic radii.

(52) In some embodiments, vacant lattice sites (0 electrons) may also be incorporated into the tetrahedral framework of Grimm-Summerfeld rules. An example is γ-Ga.sub.2S.sub.3 which is a 3.sub.206.sub.3 type. Aluminum vacancies in AlN may be considered a quadruplet of non-bonding orbitals (lone pairs) in the tetrahedral structure. Aluminum vacancies in AlN may increase viscoelastic losses (especially if mobile) or enhance piezoelectric distortion without increasing ionicity.

(53) Other compounds which may be useful in mixing with AlN to form a doped AlN material include the 4.sub.305.sub.4 compounds such as Si.sub.3N.sub.4 and Ge.sub.3N.sub.4. Ge.sub.3N.sub.4 crystallizes in a defect-containing Wurtzite structure where cation vacancies are ordered. Increasing p orbital character in non-bonding orbitals leads to the tendency for sp.sup.2 (planar) hybridization of bonding orbitals which may distort lattice the crystal lattice. Solid solutions such as Al.sub.1−xGe.sub.3/4x□.sub.1/4xN and Al.sub.1−xSi.sub.3/4x□.sub.1/4xN are also of interest, where □ represents a vacancy in an Al site of the crystal structure of the piezoelectric material.

(54) In solid solutions of AlN with GaN and InN, k.sup.2 and sound velocity are expected to drop. The dielectric constant of the material may therefore increase slightly relative to un-doped AlN along with the c/a ratio due to assumed linear relationships in properties.

(55) The expected effect of various dopants on various material properties of AlN are tabulated in FIG. 16.

(56) A listing of different AlN based piezoelectric materials that may exhibit desirable properties for use in acoustic wave resonators or filters and the expected effect of the dopant(s) on the base AlN material is presented in Table 2 below:

(57) TABLE-US-00002 TABLE 2 Compound Formula Expected Effect of Dopant(s) Al.sub.1−x(Sm.sup.3+ . . . Yb.sup.3+).sub.xN Yb.sup.3+ is larger more electropositive ion than Sm.sup.3+ . . . Yb.sup.3+ = any one or more of the Sc.sup.3+ and smaller and more electropositive than Lanthanides with atomic numbers from Y.sup.3+. 62-70. Sm.sup.3+ is larger and more electropositive than both Sc.sup.3+ and Y.sup.3+ and has a high Shannon polarizability to improve dielectric constant. As dopant level increases, expect to decrease Q and increase k.sup.2 and dielectric constant. The sound velocity should decrease as well. Higher ionicities than Sc—N bond. Expect higher dielectric constants than Sc doped AlN. Al.sub.1−x−yB.sub.xM.sup.III.sub.yN Boron and M.sup.III will work in opposite directions. M.sup.III = Sc.sup.3+, Y.sup.3+, Sm.sup.3+ . . . Yb.sup.3+ Three different sized ions on Al site may This is a combination of boron and Sc.sup.3+ negatively impact Q. or one or more electropositive ions such as Y.sup.3+ or Yb.sup.3+. The number of cation substitutions may be limited to three or less. Al.sub.1−x−yB.sub.xCr.sup.3+.sub.yN Potential for high sound velocity material with This is a combination of boron and Cr.sup.3+. modest decreases in the coupling as compared to B substitution alone. Both B and Cr are reported to increase the sound velocity. They oppose each other with regard to k.sup.2 and ε′. Al.sub.1−x−yCr.sup.3+.sub.xM.sup.III.sub.yN Potential for a high k.sup.2 and ε′ material without M.sup.III = Sc.sup.3+, Y.sup.3+, Sm.sup.3+ . . . Yb.sup.3+ significant reduction in sound velocity or This is a combination of Cr and Sc.sup.3+ or viscoelastic losses. Improved Q a possibility. Cr one or more electropositive ions such as induces lattice strain and deforms Wurzite Y.sup.3+ or Yb.sup.3+. structure. Al.sub.1−xCo.sub.xN Co readily adapts 2+, 3+ and 4+ oxidation states and each oxidation state has multiple spin states leading to a set of potential ionic sizes. Single doping will likely lead to 3+ state but 4+ and 2+ states may be induced by co-doping with Mg.sup.2+ or Zr.sup.4+ (or Hf.sup.4+) respectively. Reduced electrical conductivity is a risk at high doping levels. Al.sub.1−xSb.sup.3+.sub.xN Sb.sup.3+ shows very high ionic polarizabilities leading to the potential for enhanced dielectric constant either for single doping or coupled doping with other ions. However, there is a risk that the Sb will adopt the Sb.sup.−3 state and substitute for Nitrogen. The effect on k.sup.2 is uncertain since the lone pair would enhance asymmetry in the Al site but the increased covalency would not. Al.sub.1−5/3xTa.sup.5+.sub.x□2/3xN Improvement in the piezoelectric coefficient □ = Aluminum vacancy expected for small additions of Ta. Al.sub.1−3xMg.sub.2xTa.sup.5.sub.xN Improvement in the piezoelectric coefficient is observed for small additions. Expect similar improvement in k.sup.2 as the Mg/Zr or Mg/Hf co-doped materials with higher ε′ due to higher polarizability than Zr or Hf. Acoustic velocity effect unknown. Al.sub.1−5/3x−3yMg.sup.2+.sub.2yTa.sup.5+.sub.x+y□2/3xN There can be a continuous series of Ta additives compensated by vacancies and Mg.sup.2+. Expect similar improvement in k.sup.2 as the Mg/Zr or Mg/Hf co-doped materials with higher ε′ due to higher polarizability than Zr or Hf. Acoustic velocity effect unknown. Al.sub.1−5/3x−3yLi.sup.+.sub.yTa.sup.5+.sub.x+y□2/3xN Expect similar improvement in k2 as the Mg/Zr or Mg/Hf co-doped materials with higher ε′ due to higher polarizability than Zr or Hf. Acoustic velocity effect unknown. Al.sub.1−5/3xNb.sup.5+.sub.x□2/3xN, Al.sub.1−3xMg.sup.2+.sub.xNb.sup.5+.sub.xN, Same chemistries as with Ta.sup.5+. Al.sub.1−5/3x−3yLi.sup.+.sub.yNb.sup.5+.sub.x+y□2/3xN, or Nb.sup.5+ more likely to be reduced than Ta.sup.5+. Al.sub.1−5/3x−3yMg.sup.2+.sub.2yNb.sup.5+.sub.x+y□2/3xN Combinations of Nb and Ta as well. Al.sub.1−xGe.sub.3/4x□1/4xN or Al.sub.1−xSi.sub.3/4x□1/4xN Possible increase in piezoelectric coefficient and Si and Ge doping. coupling without significant decrease in sound velocity. However, it is likely Si and Ge partition onto both the AlN sites without the need charge compensating defects. Covalency would increase in both cases. Al.sub.1−2xMg.sup.2+.sub.xSi.sup.4+.sub.xN Using Mg.sup.2+ to bias Si into Al site for charge compensation. Possible double effect on k.sup.2 and d.sub.33. Large electropositive ions will boost k.sup.2. The Si.sup.4+ may behave as a small charged ion (as in doped ZnO) and contribute to the k.sup.2. More likely, it will enhance covalence and potentially give a solution with enhanced k.sup.2 without the sound velocity degradation and viscoelastic losses. Al.sub.1−2xMg.sup.2+.sub.xTi.sup.4+.sub.xN Ti.sup.3+ may forms and Mg.sub.Al may be charge compensated with Magnesium vacancies. d.sup.0 states in 1st row transition metals such as Ti.sup.4+ and V.sup.5+ unlikely to be stabilized in AlN.

(58) As discussed above, the various materials disclosed herein may be useful as piezoelectric materials in BAW resonators. In some implementations, the various materials disclosed herein may also be useful as piezoelectric materials in surface acoustic wave (SAW) resonators or filters. One type of BAW resonator is a solidly mounted resonator (SMR). One example of an SMR BAW is illustrated in FIG. 17, generally at 100. The SMR BAW is formed on a substrate 105, for example, a silicon substrate. A layer of piezoelectric material 110 is disposed on the substrate 105 between an upper electrode 115 and a lower electrode 120. The layer of piezoelectric material 110 may include or consist of any of the materials disclosed herein. The layer of piezoelectric material 110 has a thickness of λ/2, where X is the resonant frequency of the SMR BAW 100. A Bragg reflector or acoustic mirror 125 including alternating layers of high impedance material 130, for example, SiO.sub.2, and low impedance material 135, for example, Mo or W, is disposed below the lower electrode 120 and helps confine acoustic energy to the piezoelectric material 110 rather than leaking away through the substrate 105. Each layer of material 120, 135 may have a thickness of λ/4.

(59) An example of an FBAR BAW is illustrated in FIG. 18, generally at 200. The FBAR BAW 200 includes a piezoelectric material film 210 disposed on a substrate 205, for example, a silicon substrate, between an upper electrode 215 and a lower electrode 220. A cavity 225 is formed below the piezoelectric material film 210 (and optionally below the lower electrode 220) and above the upper surface of the substrate 205 to allow for the piezoelectric material film 210 to vibrate. The piezoelectric material film 210 may include or consist of any of the materials disclosed herein.

(60) Examples of SMR BAW and/or FBAR BAW resonators including any of the materials disclosed herein as their piezoelectric elements may be combined together to form a filter. One example of a filter arrangement that may be useful in filtering signals in the radio frequency (RF) range may be a ladder filter 300 as illustrated schematically in FIG. 19. The ladder filter 300 includes a plurality of series resonators R1, R2, R3, R4, R5, R6 connected in series between an input port 305 and an output port 310 and a plurality of parallel resonators R7, R8, and R9 having first sides electrically connected between a pair of the series resonators and second sides electrically connected to a reference voltage, for example, ground. The resonant and anti-resonant frequencies of the resonators R1-R9 may be selected such that the ladder filter 300 passes RF energy within a desired passband from the input port 305 to the output port 310 while attenuating RF energy at frequencies outside of the passband. It should be appreciated that the number and arrangement of series and/or parallel resonators included in the ladder filter may vary based on the desired frequency response of the filter.

(61) Referring to FIG. 20, there is illustrated a block diagram of one example of a front-end module 400, which may be used in an electronic device such as a wireless communications device (e.g., a mobile phone) for example. The front-end module 400 includes an antenna duplexer 410 having a common node 412, an input node 414, and an output node 416. An antenna 510 is connected to the common node 412. The front-end module 400 further includes a transmitter circuit 432 connected to the input node 414 of the duplexer 410 and a receiver circuit 434 connected to the output node 416 of the duplexer 410. The transmitter circuit 432 can generate signals for transmission via the antenna 510, and the receiver circuit 434 can receive and process signals received via the antenna 510. In some embodiments, the receiver and transmitter circuits are implemented as separate components, as shown in FIG. 20; however in other embodiments these components may be integrated into a common transceiver circuit or module. As will be appreciated by those skilled in the art, the front-end module 400 may include other components that are not illustrated in FIG. 20 including, but not limited to, switches, electromagnetic couplers, amplifiers, processors, and the like.

(62) The antenna duplexer 410 may include one or more transmission filters 422 connected between the input node 414 and the common node 412, and one or more reception filters 424 connected between the common node 412 and the output node 416. The passband(s) of the transmission filter(s) are different from the passband(s) of the reception filters. Each of the transmission filter(s) 422 and the reception filter(s) 424 may include one or more resonators including one or more embodiments of the piezoelectric material as disclosed herein. An inductor or other matching component 440 may be connected at the common node 412.

(63) In certain examples, each of the acoustic wave elements used in the transmission filter 422 or the reception filter 424 include the same piezoelectric material. This structure reduces the effect of changes in temperature upon the frequency responses of the respective filter, in particular, reducing degradation in the passing or attenuation characteristics due to changes in the temperature, because each acoustic wave element changes similarly in response to changes in the ambient temperature.

(64) FIG. 21 is a block diagram of one example of a wireless device 500 including the antenna duplexer 410 shown in FIG. 20. The wireless device 500 can be a cellular phone, smart phone, tablet, modem, communication network or any other portable or non-portable device configured for voice or data communication. The wireless device 500 can receive and transmit signals from the antenna 510. The wireless device includes an embodiment of a front-end module 400′ similar to that discussed above with reference to FIG. 20. The front-end module 400′ includes the duplexer 410, as discussed above. In the example shown in FIG. 21 the front-end module 400′ further includes an antenna switch 450, which can be configured to switch between different frequency bands or modes, such as transmit and receive modes, for example. In the example illustrated in FIG. 21, the antenna switch 450 is positioned between the duplexer 410 and the antenna 510; however, in other examples the duplexer 410 can be positioned between the antenna switch 450 and the antenna 510. In other examples the antenna switch 450 and the duplexer 410 can be integrated into a single component.

(65) The front end module 400′ includes a transceiver 430 that is configured to generate signals for transmission or to process received signals. The transceiver 430 can include the transmitter circuit 432, which can be connected to the input node 414 of the duplexer 410, and the receiver circuit 434, which can be connected to the output node 416 of the duplexer 410, as shown in the example of FIG. 20.

(66) Signals generated for transmission by the transmitter circuit 432 are received by a power amplifier (PA) module 460, which amplifies the generated signals from the transceiver 430. The power amplifier module 460 can include one or more power amplifiers. The power amplifier module 460 can be used to amplify a wide variety of RF or other frequency-band transmission signals. For example, the power amplifier module 460 can receive an enable signal that can be used to pulse the output of the power amplifier to aid in transmitting a wireless local area network (WLAN) signal or any other suitable pulsed signal. The power amplifier module 460 can be configured to amplify any of a variety of types of signal, including, for example, a Global System for Mobile (GSM) signal, a code division multiple access (CDMA) signal, a W-CDMA signal, a Long Term Evolution (LTE) signal, or an EDGE signal. In certain embodiments, the power amplifier module 460 and associated components including switches and the like can be fabricated on gallium arsenide (GaAs) substrates using, for example, high-electron mobility transistors (pHEMT) or insulated-gate bipolar transistors (BiFET), or on a Silicon substrate using complementary metal-oxide semiconductor (CMOS) field effect transistors.

(67) Still referring to FIG. 21, the front-end module 400′ may further include a low noise amplifier module 470, which amplifies received signals from the antenna 510 and provides the amplified signals to the receiver circuit 434 of the transceiver 430.

(68) The wireless device 500 of FIG. 21 further includes a power management sub-system 520 that is connected to the transceiver 430 and manages the power for the operation of the wireless device 500. The power management system 520 can also control the operation of a baseband sub-system 530 and various other components of the wireless device 500. The power management system 520 can include, or can be connected to, a battery (not shown) that supplies power for the various components of the wireless device 500. The power management system 520 can further include one or more processors or controllers that can control the transmission of signals, for example. In one embodiment, the baseband sub-system 530 is connected to a user interface 540 to facilitate various input and output of voice and/or data provided to and received from the user. The baseband sub-system 530 can also be connected to memory 550 that is configured to store data and/or instructions to facilitate the operation of the wireless device, and/or to provide storage of information for the user.

(69) Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. It is to be appreciated that embodiments of the methods and apparatuses discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the foregoing description or illustrated in the accompanying drawings. The methods and apparatuses are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. One or more features of any embodiment disclosed herein may be added to or substituted for any one or more features of any other embodiment. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. Any references to front and back, left and right, top and bottom, upper and lower, and vertical and horizontal are intended for convenience of description, not to limit the present systems and methods or their components to any one positional or spatial orientation. Accordingly, the foregoing description and drawings are by way of example only.