The different electrical responses of HgCdTe and InSb photovoltaic infrared detectors under pulsed laser irradiation

摘要

In the experiments of photovoltaic detectors illuminated by CW lasers, some new mechanism has been found, such as power saturation of photovoltage, hot carrier effect, as well as thermovoltage effect. To investigate whether there is similar mechanism with pulsed laser irradiating, an 808nm femtosecond pulsed laser is adopted. In the experiments, three photovoltaic infrared detectors are used, namely short wavelength HgCdTe detector, medium wavelength HgCdTe detector and medium wavelength InSb detector. Actually, the 808nm pulsed laser is spectral related laser for short wavelength HgCdTe detector while spectral unrelated laser for medium wavelength HgCdTe and InSb detector. Under various power densities, the detectors have a series of outputs. Power saturation of photovoltage is observed. However, the characteristics of the outputs of these three detectors are quite different, even between medium wavelength HgCdTe and InSb detector, which have the same packing method. There are three major contributions in the paper. Firstly, explain the mechanism of power saturation of photovoltage, mainly from hot carrier effect and the depressed ability of PN junction to separate electrons and holes with the higher temperature induced by the laser. Secondly, compare the differences between medium wavelength HgCdTe and InSb detector and give a qualitative analysis. Finally, the difference of the outputs between short and medium wavelength HgCdTe detector is compared and qualitatively analyzed, too, with the different mechanisms of interaction between infrared detectors and spectral related or spectral unrelated laser. The experimental results and theory analysis will show valuable clue for future research on photovoltaic detector irradiated by pulsed laser.