Epitaxial growth of HgCdTe on sapphire for photoconductive detectors

We used a combination of isothermal vapor phase epitaxy (ISOVPE) and liquid phase epitaxy (LPE) to grow HgCdTe on a CdTe/sapphire substrate by metal organic chemical vapor deposition (MOCVD). ISOVPE was used to convert a CdTe layer to Hg 0.8 Cd 0.2 Te. The ISOVPE and LPE processes were consecutive and performed in a closed tube. Using the conversion process, the lattice mismatch between CdTe and HgCdTe decreases. The conversion also reduces the compositional gradient caused by interdiffusion between the CdTe substrate and the epitaxial layer. After annealing the wafer in a Hg atmosphere, performance as a photoconductive detector was used to examine the wafer quality. The results are comparable to the performance of conventional detectors made of LPE-grown HgCdTe on CdZnTe.