Epitaxial HgCdTe/CdTe Photodiodes For The 1 To 3 μm Spectral Region

Hg_l__xCd_x/cTe epitaxial layers have been successfully grown in various compositions, for 1-3 μm applications. n⁺/p junctions are formed either by a standard B-implantation into as-grown p-type layers or by doubly grown p- and n-layers. The SWIR HgCdTe photodiodes exhibit quantum efficiencies of 55-65% without AR coating. For the diodes with 1.39 μm cut-off at room temperature, the zero bias detector resistance-area (R_οA) product is 4 x 10⁴ Q-cm², and the dark current density is - 1 x 10^-4 Ω-cm² at half-breakdown voltage. The same values of - 104 Ω-cm² R_oA products have also been measured for 2.4 μm cut-off photodiodes at 195K. The energy gap and temperature dependence of RoA product is in excellent agreement with the bulk limited generation-recombination model. The breakdown voltages of SWIR diodes vary from 12 volts to greater than 130 volts, depending on the Cd composition (x) and base carrier concentrations.