Power photodiode structures, methods of making, and methods of use
According to the present disclosure, techniques related to manufacturing and applications of power photodiode structures and devices based on group-III metal nitride and gallium-based substrates are provided. More specifically, embodiments of the disclosure include techniques for fabricating photodiode devices comprising one or more of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, structures and devices. Such structures or devices can be used for a variety of applications including optoelectronic devices, photodiodes, power-over-fiber receivers, and others.
1. A photodiode structure, comprising:
a substrate having a first surface and a second surface, wherein
the second surface is opposite to the first surface,
the substrate is a single-crystalline group-III metal nitride, and
the first surface of the substrate has a crystallographic orientation within 5 degrees of (0001) +c-plane, {10-10} m-plane, or a semipolar plane selected from one of {11-2±2}, {60-6±1}, {50-5±1}, {40-4±1}, {30-3±1}, {50-5±2}, {70-7±3}, {20-2±1}, {30-3±2}, {40-4±3}, {50-5±4}, {10-1±1}, {1 0 −1 ±2}, {1 0 −1 ±3}, or differs from (000-1) by between 2 degrees and 5 degrees;
an n-type layer and a p-type layer that are disposed over the first surface of the substrate, wherein the n-type layer and the p-type layer each comprise Al x In y Ga 1-x-y N, where 0≤x, y, x+y≤1, and have a dopant concentration of at least 1×10 16 cm −3 ;
one or more absorber layers disposed between the n-type and the p-type layers, wherein the one or more absorber layers comprise Al x In y Ga 1-x-y N, where 0≤x, y, x+y≤1 and have a dislocation density below about 10 9 cm −2 ;
a p-side electrical contact layer disposed over the p-type layer, wherein the p-side electrical contact layer has an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 3×10 −3 Ωcm 2 ;
an n-side electrical contact layer disposed over the second surface of the substrate, wherein the n-side electrical contact layer has an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 1×10 −3 Ωcm 2 ; and
a light receiving surface, wherein the light receiving surface is aligned to cause light, having at least one wavelength between 390 nanometers and 460 nanometers and incident on the light receiving surface at an angle, to be reflected at least once from the n-side electrical contact layer and from the p-side electrical contact layer, wherein the photodiode structure is characterized by a fill factor of at least 50%.
2. The photodiode structure of claim 1 , wherein the fill factor is achieved under an illumination level producing a current density of at least 10 A cm −2 .
3. The photodiode structure of claim 1 , wherein the fill factor is at least 80%.
4. The photodiode structure of claim 1 , wherein the fill factor is at least 90%.
5. The photodiode structure of claim 1 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of (0001) +c-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×10 19 cm −3 .
6. The photodiode structure of claim 1 , further comprising at least one of an n-type cladding layer and a p-type cladding layer, wherein
the n-type cladding layer lies between the n-type layer and the one or more absorber layers,
the n-type cladding layer has a dopant concentration of at least 5×10 18 cm −3 ,
the p-type cladding layer lies between the one or more absorber layers and the p-type layer, and
the p-type cladding layer has a dopant concentration of at least 1×10 19 cm −3 .
7. The photodiode structure of claim 1 , further comprising:
at least one of an n-type cladding layer and a p-type cladding layer,
the n-type cladding layer lying between the n-type layer and the one or more absorber layers, and
the p-type cladding layer lying between the one or more absorber layers and the p-type layer,
wherein the at least one of the n-type cladding layer and the p-type cladding layer is characterized by an indium concentration intermediate between that of the one or more absorber layers and that of the n-type layer or p-type layer.
8. The photodiode structure of claim 1 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation that differs from (000-1) −c-plane by between 2 degrees and 5 degrees.
9. The photodiode structure of claim 1 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of {10-10} m-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 2×10 18 cm −3 .
10. The photodiode structure of claim 1 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of a semipolar plane selected from {10-1-2}, {10-1-1}, {20-2-1}, and {30-3-1} and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×10 18 cm −3 .
11. The photodiode structure of claim 1 , wherein
the p-side electrical contact layer is disposed over the p-type layer, and
has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 1×10 −3 Ωcm 2 .
12. The photodiode structure of claim 1 , wherein the n-side electrical contact layer has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 5×10 −4 Ωcm 2 .
13. The photodiode structure of claim 1 , wherein each of the n-type layer, the one or more absorber layers, and the p-type layer have a threading dislocation density below 10 7 cm −2 .
14. The photodiode structure of claim 1 , wherein each of the n-type layer, the one or more absorber layers, and the p-type layer have a threading dislocation density below 10 6 cm −2 .
15. A photodiode structure, comprising:
one or more absorber layers, wherein the one or more absorber layers comprise Al x In y Ga 1-x-y N, where 0≤x, y, x+y≤1;
an n-type layer and a p-type layer, wherein
the one or more absorber layers are disposed over the n-type layer,
the p-type layer is disposed over the one or more absorber layers, and
the n-type layer and the p-type layer each comprise Al x In y Ga 1-x-y N, where 0≤x, y, x+y≤1, and have a dopant concentration of at least 1×10 16 cm −3 ;
a carrier substrate having a first surface and a second surface, wherein
the first surface of the carrier substrate is disposed over the p-type layer or under the n-type layer, and
the carrier substrate is substantially transparent at wavelengths between 390 nanometers and 460 nanometers;
a p-side electrical contact layer placed in electrical contact with the p-type layer, wherein the p-side electrical contact layer has a contact resistance below 3×10 −3 Ωcm 2 ;
a p-side reflector layer disposed on one of the p-type layer and the second surface of the carrier substrate, the p-side reflector layer having an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers;
an n-side electrical contact layer placed in electrical contact with the n-type layer, wherein the n-side electrical contact layer has a contact resistance below 1×10 −3 Ωcm 2 ;
an n-side reflector layer disposed over one of an n-side layer and the second surface of the carrier substrate, the n-side reflector layer having an average reflectance of at least 70% for at least one wavelength between 390 nanometers and 460 nanometers; and
a light receiving surface, wherein the light receiving surface is aligned to cause light, having at least one wavelength between 390 nanometers and 460 nanometers and incident on the light receiving surface at an angle, to be reflected at least once from the n-side reflector layer and from the p-side reflector layer, wherein the photodiode structure is characterized by a fill factor of at least 50%.
16. The photodiode structure of claim 15 , wherein the fill factor is achieved under an illumination level producing a current density of at least 10 A cm −2 .
17. The photodiode structure of claim 15 , wherein the fill factor is at least 80%.
18. The photodiode structure of claim 15 , wherein the fill factor is at least 90%.
19. The photodiode structure of claim 15 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of (0001) +c-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×10 19 cm −3 .
20. The photodiode structure of claim 15 , further comprising at least one of an n-type cladding layer and a p-type cladding layer, wherein
the n-type cladding layer lies between the n-type layer and the one or more absorber layers,
the n-type cladding layer has a dopant concentration of at least 5×10 18 cm −3 ,
the p-type cladding layer lies between the one or more absorber layers and the p-type layer, and
the p-type cladding layer has a dopant concentration of at least 1×10 19 cm −3 .
21. The photodiode structure of claim 15 , further comprising:
at least one of an n-type cladding layer and a p-type cladding layer,
the n-type cladding layer lying between the n-type layer and the one or more absorber layers, and
the p-type cladding layer lying between the one or more absorber layers and the p-type layer,
wherein the at least one of the n-type cladding layer and the p-type cladding layer is characterized by an indium concentration intermediate between that of the one or more absorber layers and that of the n-type layer or p-type layer.
22. The photodiode structure of claim 15 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation that differs from (000-1) −c-plane by between 2 degrees and 5 degrees.
23. The photodiode structure of claim 15 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of {10-10} m-plane and each of the n-type and p-type layers are characterized by a dopant concentration of at least 2×10 18 cm −3 .
24. The photodiode structure of claim 15 , wherein each of the one or more absorber layers, the n-type layer, and the p-type layer are characterized by a crystallographic orientation within 5 degrees of a semipolar plane selected from {10-1-2}, {10-1-1}, {20-2-1}, and {30-3-1} and each of the n-type and p-type layers are characterized by a dopant concentration of at least 1×10 18 cm −3 .
25. The photodiode structure of claim 15 , wherein the p-side electrical contact layer:
is disposed over the p-type layer, and
has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 1×10 −3 Ωcm 2 .
26. The photodiode structure of claim 15 , wherein the n-side electrical contact layer has an average reflectance of at least 80% for at least one wavelength between 390 nanometers and 460 nanometers and a contact resistance below 5×10 −4 Ωcm 2 .