Temperature gradient solution zoning growth and characterization of Zn_xCd_1-xSe single crystals

Single crystals of Zn_xCd_1-xSe with 0 ≤ x ≤ 0.3 have been grown from a high temperature Se solution using the TGSZ technique. The Zn/Cd distribution has been measured using an original XRF analysis system and found uniform throughout any particular crystal. The dark resistivity of Zn_0.3Cd_0.7Se crystals (5 × 10⁷ ohm cm) is higher than that of CdSe crystals (10⁶ ohm cm) grown by the same method, due to the larger energy band gap of the ternary compound. A discrete electron trapping level located 0.49 eV below the conduction band with a trap density of 1.9 × 10¹¹ cm^-3 has been attributed to a compensated donor formed by an interstitial Cu impurity and a nearby Cd vacancy. The charge collection efficiency has been studied as a function of voltage applied to a thin Zn_0.3Cd_0.7Se platelet. It is not limited, however, by the electron traps, but rather by the surface recombination of charge carriers. It has been suggested that an improved charge collection needed for the fabrication of (Zn,Cd) Se nuclear radiation detectors can be obtained by reduction of surface defects generated during the crystalline platelet processing.