Articles you may be interested inThe effects of deep level traps on the electrical properties of semi-insulating CdZnTe approached the neutral axis, so this hypothesis cannot be fully checked. It must be pointed out that the observations here do not constitute a new measurement of the "starting stress" (because this measurement depends upon the patience of the observer), but rather emphasizes a pitfall in the measurement of this property. CONCLUSIONSIt is concluded that the sense of stress state has no effect upon the properties of plastic deformation on the second order pyramidal system in zinc. In this investigation dislocation velocity was found to be unaffected by a change from a compression to a tension stress 8tate. The stress-strain curves obtained by Stofel and Wood 3 and the "starting stress" measurements of Lavrent'yev et al. 5 reveal no essential difference be-JOURNAL OF APPLIED PHYSICS tween the deformation behavior in tension and compression. These observations contradict those reported by Gilman. 2 Dislocation velocity was measured in this investigation at stresses small in comparison with the "starting stress" reported by Lavrent'yev et al. The very small dislocation displacements detected by those investigators were not the equilibrium displacements and therefore their measurements did not give a true value of the "starting stress."The transport of charge in single crystals of semi-insulating cadmium telluride has been studied under the influence of deep trapping and subsequent thermal release of carriers from traps. Trapping and detrapping times for electrons and holes are determined directly from the shape of the transient response of surface-barrier devices to alpha particles. Hole-trapping times are 60 nsec; electron-trapping times range from 30 to 90 nsec. The measurement of the detrapping times from _60° to 60° C indicates that an electron trap with an activation energy of 0.59±0.04 eV can exist below the conduction band in semi-insulating material. The present measurement of drift mobilities, trap densities, and trapping cross sections does not require observation of a transit time. Furthermore, pulse analysis is not limited to times less than the transit time, a restriction in previous drift measurements. The theoretical response which accounts for both the trapping and detrapping of charge was derived by solving the kinetic differential equations which represent charge conservation. This extends the small-signal theory of transient currents in insulators to times beyond the transit time. Excellent agreement is found between experimental traces and theoretical shapes using a single-level trap model. Limiting cases which allow convenient measurement of the material parameters are described. In addition, the energy required to form an electron-hole pair is redetermined and found to be 4.9±0.1 eV.

The results of the variation of discharge current under pulsed illumination are presented, and their bearing on the underlying mechanism is pointed out.

Three glow peaks, named cc, p, and y, of TSEE from CaSO, previously excited with X-ray or UV light were observed a t temperatures of about 110, 150, and 200 "C. The p peak is most intense among these three peaks in case of X-ray excitation, but on the contrary, the y peak is most intense for excitation with UV light. Only the electrons trapped in the p traps are able t o be optically stimulated as OSEE, and electrons in other traps are not. It is proposed that the p traps are uniformly distributed in the crystals but the y traps are localized in surface layers of the crystals. The cc traps are unclarified as yet. Drei Glowmaxima, cc, p und y, von thermisch angeregten Exoelektronen von CaSO,, das kurzzeitig durch Rontgenstrahlen oder ultraviolettes Licht angeregt wurde, werden bei Temperaturen von etwa 110,150 und 200 "C beobachtet. Das P-Maximum ist das intensivste dieser drei Maxima im Falle der Rontgenstrahlen-Anregung. I m Gegensatz dazu steht das y-Maximum, das a m intensivsten ist, wenn es mit UV-Licht angeregt wird. Kin die Elektronen, die in P-Haftstellen eingefangen werden, konnen optisch angeregt werden zu Exoelektronen, wihrend dies bei Elektronen in anderen Haftstellen nicht der Fall ist. Es wird angenommen, daS die P-Haftstellen gleichmaI3ig im Kristall verteilt und die y-Haftstellen an der Oberflache des Kristalls lokalisiert sind. Die cc-Haftstellen sind bisher noch ungeklart.

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