Properties of long wavelength (Hg, Cd) Te photodiodes in epitaxial films

This paper reports the material and device characteristics of epitaxial HgCdTe/CdTe heterostructures with cut-off wavelength from 8 to 14 µm at 77K. The HgCdTe layer was grown by a vertical dipping liquid phase epitaxy (LPE) technique. The as-grown layers were p-type with hole concentration on the order of 10¹⁷cm^-3. The layers exhibited exceptionally good composition uniformity; Cd composition varied < ±1% across a 1.5 × 1.5 cm sample. n⁺-p junctions in the epitaxial layer were obtained by ion-implantation. Spectral response of the devices was obtained by illuminating through the CdTe substrates. External quantum efficiency of ∼40% was measured on samples even without anti-reflection coating. The RoA products of the epitaxial diodes are currently comparable to those of the bulk diodes.