COMPARISON OF IN1-XTIXSB AND HG1-XCDXTE AS LONG-WAVELENGTH INFRARED MATERIALS

Cohesive energies, elastic constants, band structures, and phase diagr am are calculated to evaluate the In1-xTlxSb alloy (ITA) as a long-wav elength infrared (LWIR) material compared to Hg1-xCdxTe (MCT). To obta in a 0.1 eV gap at zero temperature, the x value for ITA is estimated to be x = 0.083 as compared to x = 0.222 for MCT. At this gap, ITA is more robust than MCT because the cohesive energies order as InSb>TlSb> CdTe>HgTe, and ITA has the stronger bonding InSb as the majority compo nent. Although TlSb is found to favor the CsCl structure, ITA is a sta ble alloy in the zincblende structure for low x values. However, our p hase diagram indicates that it is difficult to grow the 0.1 eV gap ITA from the melt, because above the eutectic the liquidus curve is flat, and the solidus drops rapidly. Moreover, the width of the stable conc entration range of the zincblende solid phase shrinks at low temperatu res due to the presence of the CsCl structure.