Defect Chemistry and Intrinsic Carrier Concentration for Hg\u3csub\u3e1-x\u3c/sub\u3eCd\u3csub\u3ex\u3c/sub\u3eTe(s) for x=0.20, 0.40 and 1.0

It has been known experimentally that crystals of Hg1-XCdXTe(s) with x ≤ 0.40 and not intentionally doped can be made with an excess of conduction band electrons over valence band holes only by equilibrating the crystals in the low temperature range so that they are as metal e.g. Hg-Cd, rich as possible or nearly so. The upper limit of this temperature range for x ≤ 0.40 ie somewhat above 300°c. The lower limit is determined by the rate of interdiffusion and the thickness of the crystals and thus far has been above 200°c. This method has been applied to the fabrication of (HgCd)Te photoconductive detectors for years without an overall understanding of the defect chemistry of the ternary compound semiconductor. On the other band, it is known that Cd - saturated CdTe is n-type for temperature as high as 900°c. It is, therefore, necessary to understand the electronic properties of these semiconductor materials and their defect structure as well as the equilibrium thermodynamic parameters for various x-values. In this investigation, the systematic approach to this problem for x = 0.20, 0.40 and 1.0 will be reviewed and developed further