Influence of native defects on the infrared transmission of undoped Ga1−xInxSb bulk crystals

Abstract

The below bandgap infrared transmission (up to 25 µm) in undoped Ga 1-x In x Sb bulk crystals has been studied for the first time and found to be limited by native defects such as antisites and vacancies found in antimonide-based III-V compounds. For the gallium-rich alloy compositions (x Ͻ 0.5 in Ga 1-x In x Sb), the crystals exhibit p-type conductivity with an increase in net acceptor concentration and an increase in gallium content in the crystals. For x Ͼ 0.5 (the indium-rich alloy compositions), the crystals exhibit n-type conductivity when the net donor concentration and indium content in the crystals increase. A correlation between the optical transmission and the residual carrier concentration arising from the native acceptors and donors has been observed. Due to donor-acceptor compensation, crystals with alloy compositions in the range of x ϭ 0.5-0.7 exhibit high optical transmission for a wide wavelength range (up to 22 µm). The light hole to heavy hole interband transition in the valence band and the free electron absorption in the conduction band have been found to be the two dominant absorption processes.

Electrical and Optical Characterization of Melt-Grown Bulk InAs1−y P y Crystals

“…Also, there is no observed decrease in transmission with increasing wavelength, clearly demonstrating the high optical quality of the grown crystals and low native defect content. These observations indicate that these InAsP wafers show improved optical quality over other III-V bulk ternary alloys such as InGaSb reported earlier, [15][16][17][18][19][20] where a significant reduction in transmission was seen even for wavelengths corresponding to photon energies below the bandgap energy. It is also interesting to mention that the transmission spectra for these wafers are not affected by the local compositional inhomogeneity seen in Fig.…”