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

• Short-wavelength infrared HgCdTe devices grown on CdTe/Si substrates have been demonstrated.
• Data suggests diffusion current dominates near zero bias for large area devices.
• Shunt current dominates reverse bias dark current in small devices.

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 2.25 μm at 300 K which corresponds to a cadmium composition of 47%. As-grown epilayers have void defect densities less than 103 cm−2 and etch pit densities of ∼1 × 107 cm−2. The Hall mobilities of annealed MCT samples are on the order of 1500 cm2/Vs and have carrier concentrations of ∼1 × 1016 cm−3 at 300 K. Samples were doped in situ with indium (donor) and ion-implanted with arsenic (acceptor) to fabricate p–n diodes with sizes ranging from 15 μm to 250 μm 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.