Patent ID: 8372685

Claim:
A method comprising: providing a bandgap grading material comprising an alloy of: a) a IIIA material and b) a group IA-based material, wherein the alloy has a higher melting temperature than a melting temperature of the IIIA material in elemental form; depositing a precursor material on a substrate to form a precursor layer, the precursor material comprising particles from group IB, IIIA, and/or VIA; and depositing the bandgap grading material of the alloy after depositing the precursor material; heating the precursor material and the bandgap grading material; wherein the alloy in the bandgap grading material reacts after the precursor layer has begun to sinter and thus maintains a higher concentration of IIIA material in a portion of a compound film that forms above a portion that sinters first; heating the precursor material at a first temperature profile, wherein the precursor layer at least partially sinters at the first temperature profile where a temperature is lower than a reacting temperature of the alloy; and increasing processing temperature to a second temperature sufficient to melt the particles of the alloy, wherein the alloy reacts after the precursor layer has begun to at least partially sinter.