Development and fabrication of extended short wavelength infrared HgCdTe sensors grown on CdTe/Si substrates by molecular beam epitaxy

Abstract

The development and fabrication of extended short-wavelength infrared (SWIR) HgCdTe (MCT) sensors grown on CdTe/Si substrates is reported. The MCT epilayers were grown on CdTe/Si substrates by molecular beam epitaxy (MBE). The epilayers were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray double crystal rocking curve (DCRC), Van der Pauw Hall measurements, dislocation defect–decoration etching and Nomarski microscopy. The FTIR analysis revealed a cutoff wavelength of 2.25μm at 300K which corresponds to a cadmium composition of 47%. As-grown epilayers have void defect densities less than 103cm−2 and etch pit densities of ∼1×107cm−2. The Hall mobilities of annealed MCT samples are on the order of 1500cm2/Vs and have carrier concentrations of ∼1×1016cm−3 at 300K. Samples were doped in situ with indium (donor) and ion-implanted with arsenic (acceptor) to fabricate p–n diodes with sizes ranging from 15μm to 250μm diameter. We present the results and analysis of temperature dependent current–voltage (I–V) and quantum efficiency/responsivity measurements on the p–n diodes. In our analysis, we found that the I–V characteristics of small devices were dominated by shunt currents and quantum efficiency is limited by Shockley–Read–Hall (SRH) mechanisms.