CdTe thin films as protective surface passivation to HgCdTe layers for the IR and THz detectors

Abstract

The properties of thin CdTe cap layers grown using the hot-wall epitaxy (HWE) method under low-temperature technological conditions (T ≤ 373 K) to Hg1-xCdxTe liquid phase epitaxial layers (LPE) have been investigated. It has been shown that the CdTe films deposited using this low-temperature method, can be used as the passivation coatings for the infrared (IR) detectors based on the HgCdTe epitaxial layers grown on the CdZnTe monocrystalline substrates, not affecting the HgCdTe properties. It has been found that CdTe films with the thickness d ≥ 360 nm are continuous and possess effective protective properties in application to Hg1-xCdxTe/CdZnTe IR detectors. The manufactured photodiode detectors demonstrate relatively good parameters: the detectivity D* = 2.7 × ·1010 cmW−1Hz1/2 (T = 80 K) for the long-wave range (8–10.5 μm) IR photodiodes (x ≈ 0.22) and noise-equivalent temperature difference NRTD ≈ 20 mK for mid-wavelength (3–5 μm) photodiodes.