The cutoff wavelength and minority-carrier lifetime in implanted n+-on-bulk p Hg1−xCdxTe photodiodes

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Abstract
The cutoff wavelength λco at 77 K of implanted n+‐on‐bulk p‐type Hg1−xCdxTe photodiodes is calculated with the minority‐carrier lifetime of the bulk material as a parameter: 1.24/λco=[T+81.9/3.267×104(1+x)] {18.88−53.61x− 1/2 ln [(kT/q) μnτn]} −0.3424+1.838x+0.148x4 (eV). The composition x is obtained from the zero‐intercept transmission spectra measured at 300 K. The minority‐carrier lifetime τn of the photodiodes and its temperature dependence have been obtained from the photodiode dynamic resistance at zero‐bias voltage versus reciprocal temperature 1/T data. The temperature dependence of the minority‐carrier mobility μn is also taken into account. The results indicate that the lifetime in the bulk p‐type material is determined by Shockley–Read generation‐recombination centers. For undoped, p‐type substrates obtained from Cominco Inc., the trap energy is approximately 45 meV. Gold‐doped crystals grown by the method of solid‐state recrystallization exhibit a trap energy of the order of 30–35 meV.