Multijunction solar cells and multicolor photodetectors having an integrated edge filter
Semiconductor devices comprising a semiconductor edge filter, a first light absorbing region overlying the semiconductor edge filter and a second light absorbing region underlying the semiconductor edge filter are disclosed. The semiconductor edge filter has a high reflectivity over a first wavelength range absorbed by the overlying light absorbing region and a high transmission over a second wavelength range absorbed by the underlying light absorbing region.
1. A semiconductor structure comprising:
a semiconductor edge filter comprising a plurality of layers, wherein: each layer of the plurality of layers has a non-periodic optical thickness, a plurality of layer pairs are formed by the plurality of layers, the optical thickness of each layer pair of the plurality of layer pairs is different from the optical thickness of its adjacent layer pairs of the plurality of layer pairs, and adjacent layers of each layer pair of the plurality of layer pairs are characterized by a different refractive index;
a first light absorbing region overlying the semiconductor edge filter having a first bandgap and a first absorption spectrum; and
a second light absorbing region underlying the semiconductor edge filter having a second bandgap and a second absorption spectrum.
2. The semiconductor structure of claim 1 , wherein the semiconductor edge filter is configured to reflect light at wavelengths that can be absorbed by the first light absorbing region.
3. The semiconductor structure of claim 1 , wherein the semiconductor edge filter is configured to transmit light at wavelengths that can be absorbed by the second light absorbing region.
4. The semiconductor structure of claim 1 , wherein the first light absorbing region is characterized by a band gap within a range from 0.7 eV to 1.3 eV.
5. The semiconductor structure of claim 1 , wherein the second light absorbing region is characterized by a band gap smaller than the bandgap for the first light absorbing region.
6. The semiconductor structure of claim 1 , wherein the semiconductor edge filter is characterized by a long-wavelength cutoff within 25 nm of the absorption edge of the first light absorbing layer.
7. The semiconductor structure of claim 1 , wherein the semiconductor edge filter is characterized by a long-wavelength cutoff within a range from 900 nm (1.378 eV) to 1,400 nm (0.885 eV), from 900 nm (1.378 eV) to 1,300 nm (0.954 eV), from 900 nm (1.378 eV) to 1,200 nm (1.033 eV), or from 1000 nm (1.240 eV) to 1,150 nm (1.078 eV).
8. The semiconductor structure of claim 1 , wherein the first light absorbing region is lattice matched to Ge or to GaAs.
9. The semiconductor structure of claim 1 , wherein the first light absorbing region comprises a dilute nitride material.
10. The semiconductor structure of claim 9 , wherein the first light absorbing region comprises GaInNAsSb, GaInNAsBi, or GaInNAsSbBi.
11. The semiconductor structure of claim 9 , wherein the first light absorbing region comprises Ga 1-x In x N y AS 1-y-z Sb z , where x, y and z fall within the ranges 0≤x≤0.4, 0<y≤0.1 and 0<z≤0.2.
12. The semiconductor structure of claim 1 , wherein the semiconductor edge filter is configured to provide a normal reflectivity greater than 90% over a first wavelength range, and a normal transmissivity greater than 95% over a second wavelength range.
13. The semiconductor structure of claim 12 , wherein a full-width-half-maximum for the reflectivity of the first wavelength range is greater than 100 nm.
14. The semiconductor structure of claim 13 , wherein the second wavelength range is at wavelengths longer than the first wavelength range and wherein the second wavelength range is greater than 500 nm.
15. The semiconductor structure of claim 1 , wherein each layer has a different non-periodic optical thickness between about 5 nm and 1,300 nm, or between about 10 nm and 1,000 nm, or between about 5 nm and 250 nm.
16. The semiconductor structure of claim 1 , wherein the semiconductor edge filter comprises from 40 to 200 layers forming from 20 to 100 layer pairs.