7.4: InTlSb

7.4 InTlSb

As an alternative to the InAsSb system, InTlSb is also a potential material for ? > 8 ?m detectors. TlSb was calculated as a semimetal from the full-potential linear muffin-tin (LMTO) method within the local density approximation (LDA) [60]. By alloying TlSb with InSb, it was suggested that the bandgap of InTlSb could be varied from -1.5 to 0.26 eV. Assuming a linear dependence of the bandgap on alloy composition, InTlSb can then be expected to reach a bandgap of 0.1 eV at x = 0.08 while exhibiting similar lattice constant as InSb since the radius of Tl atom is very similar to In. To date, very limited experimental work has been reported on the growth and characterization of InTlSb. Choi et al. [61] reported on the first successful growth of InTlSb by LP-MOCVD. A bandgap shift toward a longer wavelength was observed, which suggests a concentration of 6% Tl. A group from the University of Utah reported Tl incorporation of less than 1% in InSb [62]. Recently, Karam et al. [63] reported the InTlSb films with Tl composition up to 10%. Spectral response measurements showed a photoresponse up to 14 ?m at 77K.