Evaluating electronic decay in wide band gap semiconductors using contactless thermally stimulated lifetime measurements

Electronic decay behavior in wide band gap semiconductor materials using a contactless method is observed. Experiments are performed to measure electronic decay behavior as a function of temperature and surface quality. Also a mathematical model of the observed electronic behavior is created and assists in the understanding of observed behavior.; In the first study a crystal of Cd_1−xZn_xTe (CZT) is pumped with a 5ns pulsed 1064 nm wavelength laser light and probed by a contactless method. Varying the temperature through a range of 110K to 290 K, the carrier lifetime of CZT decreased from approximately 30 microseconds at 110K to 4 microseconds at 160K, and then remained relatively constant to 290K. The sudden drop in carrier lifetime within a particular temperature range is consistent with thermal activation of a charge trap with a detrapping time longer than the carrier lifetime. The maximum trap activation temperature and the minimum detrapping time are estimated from the lifetime versus temperature curve to be approximately 160K and 10−6 s, respectively.; In the next study, a crystal of CZT that has been mechanically cut is gradually etched using a Bromine/Methanol solution. With an improvement of surface quality an increase in carrier lifetime is observed at low temperature.; To further assist us in the understanding of the observed electronic behavior in CZT a model of the electronic behavior is created. The modeled behavior plotted along side the experimental data provides a method to calculated trap energies within the band gaps of semiconductor materials. Using the model a recombination center at energy of .600–.700 eV is determined to exist from the bands edge for CZT.; The method developed from the investigation of CZT is applied to another wide band gap semiconductor, mercuric iodide. Similar investigations are performed as well as a tentative evaluation of nonstochoimetry has upon electronic behavior of mercuric iodide.