High efficiency multijunction solar cells

1. A method of manufacturing a photovoltaic cell, comprising:

forming one or more semiconductor layers on a substrate; and

forming four or more subcells overlying the one or more semiconductor layers; and

wherein at least one of the subcells has a base layer formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05, and 0.001≦z≦0.02;

wherein each of the four or more subcells is substantially lattice matched to each of the other subcells.

2. The method of claim 1 , comprising forming tunnel junctions between each of the four or more subcells.

3. The method of claim 1 , wherein the substrate is selected from the group consisting of Si, Ge, GaAs, and InP.

4. The method of claim 1 , wherein the at least one subcell is characterized by a bandgap selected from the group consisting of 0.7 eV to 1.1 eV, 0.8 to 0.9 eV, 0.9 eV to 1.0 eV, 0.9 eV to 1.3 eV, 1.0 eV to 1.1 eV, 1.0 eV to 1.2 eV, 1.1 eV to 1.2 eV, 1.1 eV to 1.4 eV, and 1.2 eV to 1.4 eV.

5. The method of claim 1 , wherein a base layer of another one of the at least four subcells is formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20.

6. The method of claim 1 , wherein a base layer of another one of the at least four subcells is formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.01≦x≦0.18, 0.005≦y≦0.05, and 0.001≦z≦0.03.

7. The method of claim 1 , wherein the at least one subcell with a base layer formed of Ga 1-x In x N y As 1-y-z Sb z has a compressive strain of less than 0.6%.

8. The method of claim 1 , wherein

the at least one subcell is a first subcell with a base layer formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05, and 0.001≦z≦0.02; and wherein a band gap of the subcell is between 0.7 and 1.1 eV; and

a second subcell has a base layer formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and wherein a band gap of the second subcell is greater than the band gap of the first subcell.

9. The method of claim 8 , wherein

the first subcell is characterized by a first band gap of 0.9 eV to 1.0 eV; and

the second subcell is characterized by a second band gap of 1.1 eV to 1.2 eV.

10. The method of claim 8 , wherein the second subcell has a base layer formed of a material selected from the group consisting of GaInNAsSb, GaInNAsBi, GaInNAsSbBi, GaNAsSb, GaNAsBi, and GaNAsSbBi.

11. The method of claim 1 , wherein forming the four or more subcells comprises:

forming a first subcell having a first base layer formed of a material selected from the group consisting of Ge, SiGe(Sn), and Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05 and 0.001≦z≦0.02, wherein the first subcell is characterized by a band gap from 0.7 eV to 1.1 eV;

forming a second subcell having a second base layer, wherein the second base layer is formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, wherein the second subcell is characterized by a band gap from 0.9 eV to 1.3 eV; and

forming at least two additional subcells overlying the second subcell;

wherein the photovoltaic cell comprises at least four subcells and each of the at least four subcells is substantially lattice matched to each of the other subcells; and

wherein the first base layer, the second base layer, or the first base layer and the second base layer are formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05 and 0.001≦z≦0.02.

12. The method of claim 11 , wherein each of the at least four subcells is substantially lattice matched to a material selected from the group consisting of Si, Ge, SiGe, GaAs, and InP.

13. The method of claim 11 , wherein

the first base layer is formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05 and 0.001≦z≦0.02; and

the second base layer is formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20.

14. The method of claim 11 , wherein forming at least two additional subcells overlying the second subcell comprises:

forming a third subcell having a third base layer is overlying the second subcell, wherein the third base layer is formed of a material selected from the group consisting GaInPAs and (Al,In)GaAs, and characterized by a band gap from 1.4 eV to 1.7 eV; and

forming a fourth subcell having a fourth base layer overlying the third subcell, wherein the fourth base layer is formed of (Al)InGaP, and characterized by a band gap from 1.9 eV to 2.2 eV.

15. A method of manufacturing a photovoltaic cell, comprising:

forming at least two subcells on a substrate;

forming a first subcell having a first base layer, wherein the first base layer is formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, v and z are 0.08≦x≦0.24, 0.02≦v≦0.05 and 0.001≦z≦0.02, wherein the first subcell is characterized by a band gap from 0.7 eV to 1.1 eV; and

forming a second subcell having a second base layer formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20 overlying the first subcell, wherein the second subcell is characterized by a band gap from 0.9 eV to 1.3 eV;

wherein each of the at least two subcells is substantially lattice matched to each of the other subcells.

16. A method of manufacturing a photovoltaic cell, comprising:

forming one or more subcells on a substrate in a first materials deposition chamber; transferring the substrate to a second materials deposition chamber; and

forming one or more additional subcells overlying the one or more subcells; and

wherein one or more of the subcells of the photovoltaic cell has a base layer formed of Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05 and 0.001≦z≦0.02; and

wherein each of the one or more subcells is substantially lattice matched to each of the other subcells.

17. The method of claim 16 , wherein molecular beam epitaxy is used to deposit a base layer of each of the one or more subcells.

18. The method of claim 16 , comprising:

forming one or more layers selected from the group consisting of a buffer layer, a contact layer, an etch stop layer, a release layer, and other semiconductor layer on the substrate in a chamber selected from the group consisting of a third materials deposition chamber and the second materials deposition chamber; and

transferring the substrate to the first materials deposition chamber.

19. The method of claim 16 , wherein the substrate is selected from the group consisting of Si, Ge, GaAs, and InP.

20. The method of claim 1 , wherein the at least one subcell is characterized by a thickness from 2 μm to 3 μm.

21. The method of claim 1 , wherein the at least one subcell is characterized by a thickness from 1.5 μm to 3.5 μm.

22. The method of claim 1 , wherein the values for x, y and z are 0.08≦x≦0.24, 0.02≦y≦0.05, and 0.001≦z≦0.02.