Comparison of the performance of quantum well and conventional bulk infrared photodetectors

Abstract

Investigations of the performance of quantum well infrared photodetectors (QWIPs) as compared o other types of semiconductor infrared detectors are presented. Two types of QWIPs are considered: GaAs/AlGaAs intersubband quantum well photoconductors and type II staggered InAs/InGaSb photodiodes. In comparative studies the HgCdTe photoconductors and photodiodes, PbSnTe photodiodes, Schottky barrier photoemissive detectors and doped silicon detectors are considered. It is assumed that the performance of HgCdTe and PbSnTe photodiodes is due to thermal generation governed by the Auger mechanism in the base regions. Investigations of the fundamental physical limitations of HgCdTe photodiodes indicate better performance of this type of detectors in comparison with GaAs/AlGaAs QWIPs operated in the range 35 to 77 K. In practice however, in temperature range below 50 K the performance of the HgCdTe photodiodes is determined by trap-assited tunneling. As a result, advantage of GaAs/AlGaAs QWIPs increases in the wider spectral range (below 14 μm) and temperature below 50 K. This observation plus the maturity of GaAs/AlGaAs technology and its radiation hard characteristics promise that QWIPs technology can produce high quality focal plane arrays (FPAs) for space applications. The operating temperature for HgCdTe detectors is higher than for other types of photondetectors. HgCdTe detectors with background limited performance operate with thermoelectric coolers in the medium wavelength range, instead the long wavelength detectors operate at ≈ 100 K. HgCdTe is characterized by high absorption coefficient and quantum efficiency and relatively low thermal generation rate compared to extrinsic detectors, silicide Schottky barriers and GaAs/AlGaAs QWIPs. However, the cooling requirments for GaAs/AlGaAs QWIPs with cutoff wavelengths below 10 μm are less stringent in comparison with extrinsic detectors and Schottky barrier devices. The theoretically predicted performance of long wavelength InAs/GaInSb photodiodes are comparable with HgCdTe photodiodes. The high performance of InAs/InGaSb detectors is due to suppression of band-to-band Auger recombination rate.