A comparison of the performance of a photovoltaic HgCdTe detector with that of large area single pixel QWIPs for infrared radiometric applications
The performance of two single pixel, large area quantum well infrared photodetectors (QWIPs) were compared with that of a commercially available 2 mm diameter photovoltaic (PV) HgCdTe detector. Parameters which were compared include the absolute spectral responsivity, noise equivalent power (NEP), spatial uniformity of response, non-linearity and stability. Both detector types were shown to have sufficiently high spectral responsivity and D* values to satisfy a number of applications in infrared radiometry when operated at 77 K. However, the spatial non-uniformity of response of both QWIPs examined was unacceptably high. Furthermore the spatial uniformity of response of the same detectors was shown to be strongly dependent on the state of polarisation of the incident radiation as well as also exhibiting some dependency on wavelength. The spatial uniformity of response of the PV HgCdTe detector was shown to be very poor due to the very low shunt resistance of this detector. However, it exhibited no polarisation dependency and only a slight dependency on wavelength for wavelengths below 5 μm. Neither detector type could be considered for high accuracy radiometric applications in their current form.