Isothermal capacitance transient spectroscopy study of deep electron traps in low resistivity melt-grown ZnSe single crystals

Deep electron traps in ZnSe crystals grown by the vertical gradient freezing method using a sealed molybdenum capsule were studied by isothermal capacitance transient spectroscopy. These crystals have electron concentrations of 10(15)-10(17) cm(-3) in the as-grown state. Besides the deep traps caused by isolated impurities, two characteristic traps were found. One is the most dominant trap in almost all samples studied, with an apparent activation enthalpy of similar to 0.3 eV accompanied by an electron capture barrier of 0.05-0.29 eV. The concentration of this trap is less than 3x10(15) cm(-3). By a deconvolution of its highly broadened spectrum, the nontheoretical emission behavior was recognized as an overlapped emission of a number of different traps with similar emission time constants. That probably corresponds to the difference of the impurity species combined with the native defect in this trap. The other trap has an activation enthalpy of 1.03-1.1 eV and the concentrations of electrons captured by the trap are found to depend logarithmically on the duration of the filling pulse. The origin of this trap is assumed to be an impurity atom associated with extended defects such as dislocations. (C) 1996 American Institute of Physics.