Multi-nary group IB and VIA based semiconductor
Methods and devices are provided for forming multi-nary semiconductor. In one embodiment, a method is provided comprising of depositing a precursor material onto a substrate, wherein the precursor material may include or may be used with an additive to minimize concentration of group IIIA material such as Ga in the back portion of the final semiconductor layer. The additive may be a non-copper Group IB additive in elemental or alloy form. Some embodiments may use both selenium and sulfur, forming a senary or higher semiconductor alloy.
1. An optoelectronic device comprising:
a thin-film absorber layer comprising a surface region, a bulk region, and a transition region disposed between the surface region and the bulk region, and
wherein the surface region includes:
a thickness of about 300 nm or less;
a Ga/(Ga+In) molar ratio that is in the range of about 0.05 to about 0.15;
a S/(Se+S) molar ratio that is in the range of about 0.1 to about 0.4; and
a Ag/(Ag+Cu) molar ratio that is in the range of about 0.05 to about 0.2.
2. The device of claim 1 wherein the thickness of the absorber layer is about 1.5 to about 2 microns.
3. The device of claim 1 wherein the thickness of the bulk region is about 0.8 to about 1.2 microns.
4. The device of claim 1 wherein the thickness of the transition region is about 0.4 to about 0.6 microns.
5. The device of claim 1 wherein a highest value of Ga/(Ga+In) molar ratio in the bulk region is at least 2× a highest value of Ga/(Ga+In) molar ratio in the transition region; a lowest value of Ga/(Ga+In) molar ratio in the transition region is at least 1.2× a lowest value of Ga/(Ga+In) molar ratio in the surface region.
6. The device of claim 5 wherein a highest value of S/(Se+S) molar ratio in the bulk region is at least 2× a highest value of S/(Se+S) molar ratio in the transition region; a highest value of S/(Se+S) molar ratio in the surface region is at least 2× the highest value of S/(Se+S) molar ratio in the transition region.
7. The device of claim 5 wherein a lowest value of Ag/(Ag+Cu) molar ratio in the bulk region is less than a lowest value of Ag/(Ag+Cu) molar ratio in the transition region; a lowest value of Ag/(Ag+Cu) molar ratio in the surface region is less than the lowest value of Ag/(Ag+Cu) molar ratio in the transition region.
8. The device of claim 5 wherein a lowest value of Ag/(Ag+Cu) molar ratio in the bulk region is at least 20% less than a lowest value of Ag/(Ag+Cu) molar ratio in the transition region; a lowest value of Ag/(Ag+Cu) molar ratio in the surface region is at least 20% less than the lowest value of Ag/(Ag+Cu) molar ratio in the transition region.
9. The device of claim 1 wherein a highest value of Ga/(Ga+In) molar ratio in the bulk region is at least 2× a highest value of Ga/(Ga+In) molar ratio in the transition region; a lowest value of Ag/(Ag+Cu) molar ratio in the surface region is at least 20% less than a lowest value of Ag/(Ag+Cu) molar ratio in the transition region.
10. The device of claim 1 wherein:
wherein surface region Ag/(Ag+Cu) molar ratio decreases at an outward surface of the surface region relative to Ag/(Ag+Cu) molar ratio in an interior portion of the surface region.
11. The device of claim 1 wherein:
wherein Ag/(Ag+Cu) molar ratio in the absorber layer has a non-linear depth profile.
12. The device of claim 1 wherein:
wherein the bulk region includes
a Ga/(Ga+In) molar ratio that is in the range of about 0.2 to about 0.6;
a S/(Se+S) molar ratio that is in the range of about 0.06 to about 0.3; and
a Ag/(Ag+Cu) molar ratio that is in the range of about 0.11 to about 0.07.
13. The device of claim 1 wherein:
the surface region S/(S+Se) molar ratio in the surface region is greater than a surface region Ag/(Ag+Cu) ratio in the surface region.
14. The device of claim 1 wherein the absorber layer further includes at least one dopant material selected from the group consisting of Na, K and Li.
15. The device of claim 1 wherein molar ratio of group IB/group IIIA in the absorber layer is in the range of 0.8-1.0.
16. The device of claim 1 wherein molar ratio of Ga/group IIIA in the absorber layer is in the range of about 0.3 to about 0.6.
17. The device of claim 1 wherein molar ratio of Ga/group IIIA in the absorber layer is in the range of about 0.25 to about 0.5.
18. The device of claim 1 wherein molar ratio of Ag/group IB in the absorber layer is in the range of about 0.1 to about 0.3.
19. The device of claim 1 wherein molar ratio of Ag/group IB in the absorber layer is in the range of about 0.05 to about 0.3.
20. The device of claim 1 wherein molar ratio of Ag/group IB in the absorber layer is in the range of about 0.05 to about 0.25.