Processing and properties of some II–IV–V₂ amorphous and crystalline semiconductors

Abstract

Experimental investigations on the preparation, characterization, and properties of several bulk and thin-film ternary alloys based on the chalcopyrite II–IV–V₂ semiconductors are presented. Rapid melt solidification in vacuum-sealed fused-silica tubes resulted in amorphous alloy formation in almost all compositions in the system CdGeAs₂-CdSiAs₂. ZnGeAs₂-CdGeAs₂ alloys showed very limited tendency toward amorphous phase formation. Phase separation, crystallization and electrical properties were studied for amorphous Cd-Ge-Si-As alloys by thermal analysis, transmission electron microscopy, X-ray diffraction, and Hall measurements. Rapid crystallization resulted in a reversal of conductivity type (p-to-n or vice versa). Crystallized glassy alloys showed room-temperature mobility of 64 cm²/V s, and a hole concentration of 1020 cm⁻³. The p-to-n change in conductivity type upon amorphous-to-crystal transformation suggests that these alloys can be used to fabricate p-n junction devices by surface crystallization of the amorphous phase.