A Review on the Development of GaSb Alternative Substrates for the Epitaxial Growth of HgCdTe

In this paper, we will review our recent effort on developing GaSb alternative substrates for growing high quality HgCdTe materials in order to fabricate next generation HgCdTe infrared detectors with unique features with higher device yields, lower production costs, and larger focal plane array format. The potential of GaSb substrate for growing HgCdTe is studied from the point view of both theoretical strain analysis and experimental investigation. Theoretically GaSb provides a better candidate substrate for growing high quality HgCdTe materials in terms of smaller mismatched strain and consequently lower dislocation density, in comparison to other alternative substrates (Si, Ge and GaAs). Experimentally, a low dislocation density (average etch pit density of similar to 1.4x10(5) cm(-2)) has been obtained for the CdTe buffer layers grown on GaSb (211) B substrates with incorporating a unique transitional buffer layer between the CdTe buffer layer and the GaSb substrate. Such a low dislocation density was achieved mainly due to significant relaxation of the lattice mismatch between the GaSb substrate and the CdTe epitaxial layer. The achieved etch pit density (similar to 1.4x10(5) cm(-2)) is well below the critical etch pit density level (5x10(5) cm(-2)) required for fabricating high performance long-wave infrared HgCdTe detectors, and is close to the etch pit density in commercial CdZnTe substrates (mid-10(4)similar to low-10(5) cm(-2)). More importantly, an even lower etch pit density can be expected with further optimizing the buffer layer technologies and implementing other treatments such as thermal annealing cycle. These results demonstrate the great potential of GaSb as the next generation alternative substrate for epitaxial growth of high quality HgCdTe infrared materials.