GAINASSB METASTABLE ALLOYS GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY

Ga//1//-//xIn//xAs//1//-//ySb//y alloys have been grown by organometallic vapor phase epitaxy using trimethyl compounds of Ga, In, As, and Sb(TMGa, TMIn, TMAs, and TMSb) plus AsH//3 in an atmospheric pressure, horizontal, infrared heated reactor. For the first time, alloys near the center of the region of solid immiscibility have been grown. Alloys with room-temperature band gaps of 0. 45 eV (Ga//0//. //6//8In//0//. //3//2As//0//. //2//8Sb//0//. //7//2) and 0. 37 eV (Ga//0//. //2//6In//0//. //7//4As//0//. //7//6Sb//0//. //2//4) have been grown on GaSb substrates and alloys with larger band gaps (0. 74 eV for Ga//0//. //7//1In//0//. //2//9As//0//. //7//6Sb//0//. //2//4) have been grown on InP substrates. The smaller band-gap alloys are grown at temperatures as low as 486 degree C. The alloys on InP substrates are grown at higher temperatures of 600 degree C, more typical of the GaAsSb and GaInAs alloys reported earlier. Solid composition was determined using energy dispersive x-ray analysis and combined x-ray diffraction and photoluminescence measurements. The low-temperature photoluminescence of these metastable alloys consists of a single, presumably band edge peak. The half-widths of the photoluminescence peaks, especially those near the center of the region of immiscibility, are broader than those for the metastable ternary alloy GaAsSb. This may indicate that a significant amount of compositional clustering occurs during growth.