Epitaxial growth of HgCdTe on sapphire for photovoltaic detectors

Abstract

We developed a technique for growing Hg07Cdo3Te on CdTc/sapphirc. Using metal organic chemical vapor deposition (MOCVD), we grew CdTe on sapphire substrates. We use a combination of isothermal vapor phase epitaxy (ISOVPE) followed by liquid phase epitaxy (LPE) to grow Flgo7Cdo3Te on them. The ISOVPE converts the surface of the CdTe layer to Hg7Cd03Te, which decreases the lattice mismatch between CdTe and HgCdTe and decreases the surface defects on HgCdTe that originate from lattice mismatching. After growth, we annealed the wafer in a Hg atmosphere to control the carier concentration. We used the peformance of photovoltaic detectors to examine the wafer quality. A typical diode with a 5-jim cutoff wavelength had an responsivity (Re) value of 2.87 AJW. The diffusion current limits R0A down to 120 K, and the generation-recombination (g-r) current limits R0A at 77 K.