Development of Electron Beam Induced Current for diffusion length determination of VLWIR HgCdTe and MWIR T2SL based photodetectors

Abstract For very high performance infrared (IR) photodetectors, characterization is necessary to understand the impact of fabrication processes. A useful tool to characterize photodetectors is the Electron Beam Induced Current (EBIC) technique. For Very-Long Wavelength InfraRed (VLWIR) HgCdTe (MCT) samples, the dark current is such that measurements can be very noisy. We develop our EBIC setup with the implementation of a cold shield and an AC operation to filter out the parasitic flux and to increase the signal to noise ratio. EBIC measurements are performed on VLWIR HgCdTe and Medium Wavelength InfraRed (MWIR) T2SL photodetectors. For the VLWIR MCT-based sample with a cut-off wavelength of 15 µm at 77 K we determine a diffusion length of 11.4 µm at 120 K while discussing the validity of theoretical models in our situation. This result is compared to a Spotscan measurement. We also determine the minority carrier diffusion length of the MWIR InAs/InAsSb based type-II superlattice (T2SL) with a cut-off wavelength of 4.5 µm at 120 K. These results are discussed in regard to the literature.