HgCdTe Long-Wavelength Infrared Photovoltaic Detectors Fabricated Using Plasma-Induced Junction Formation Technology

A long-wavelength infrared (LWIR) HgCdTe photodiode fabrication process has been developed based on reactive ion etching (RIE) plasma-induced p-to-n type conversion for junction formation. The process has been successfully applied to produce devices using both vacancy-doped and gold-doped liquid phase epitaxy (LPE)-grown p-type HgCdTe material with a cut-off wavelength of 10 mum at 77 K. The fabrication procedure is outlined and results are presented on completed devices that indicate the effect of variations in processing parameters. The fabricated devices have been characterized by measurements of the diode dark I-V characteristic over the temperature range 20-200 K, as well as by spectral responsivity measurements. Analysis of the device I-V data, variable area data, and modeling of diode dark current mechanisms indicates that gold-doped material results in higher performing devices compared to vacancy-doped material. Device performance is found to be strongly affected by trap-assisted tunneling currents and surface leakage currents at zero bias. Nonoptimum surface passivation is likely to be the major factor limiting performance at this early stage of device technology development.