Device analysis of MBE HgCdTe p-on-n photovoltaic detectors in 5- to 15-μm wavelength range

Abstract

An attempt is made to connect the material parameters of Hg 1-x Cd x Te layer growth to the parameters measured following photovoltaic detector fabrication. We found that the Cd composition X value extracted from spectral response measurements on detectors at 78 K are lower than the X values obtained from the room temperature transmission measurements, or the X value used to fit the measured material minority carrier lifetime versus temperature data. The lateral collection length L c that determines the thermally generated carriers that contribute to the diffusion current and L opt extracted from the "flood-illuminated" to "focused-spot" photocurrent ratio are in excellent agreement.Devices exhibit near theoretical R o A uniformity at 77K for MWIR, LWIR and VLWIR. R o A opt was also found to be uniform throughout the range of detector dimensions measured such as 8 µm diameter circular to 250 µm x 250 µm square. Median R o A opt values are 1266, 66 and 0.75 ohm-cm 2 for the 9.7, 11.3 and 15.4 µm cutoff wavelengths respectively. The uniformity in R o A opt confirms that the detector performance is limited by the bulk properties of the material, and not by surface effects.