E. Klier

Thermostimulated currents in n-type CdTe single crystals

Measurements of thermostimulated currents on n-type CdTe crystals yield activation energies of traps which can be identified with previously known localized levels. The diffusion of Cu and In into the crystals can be proved by means of the presence of corresponding trap levels.

Thermostimulated currents in p-type cadmium telluride single crystals

Ssveral samples of CdTe were measured in a temperature range of −190‡C to 100‡C. The activation energies of the levels and their cross-section were determined. With some samples it was found that for more rapid heating the maxima of the curves of thermostimulated currents are shifted towards lower temperatures. Altogether three trap levels were found.

Space charge limited currents in high resistivity CdTe crystals

DC-measurements of SCLC of high resistivity Cl-compensated p-type crystals of CdTe have been performed in the temperature range of 230–300 K. The evaluation of voltage-current characteristics by means of a simple model with discrete trap levels led to activation energies of approx. 0·65 and 0·4 eV above the valence band and trap concentrations of the order 1011 to 1012 cm−3.

Piezoelectric resonators of InP:Fe

Piezoelectric resonators in the form of rectangular platelets of semiinsulating InP∶Fe were produced by cleaving along direction {011} to excite fundamental longitudinal modes of vibrations. The analysis of the transfer function of such resonators in the region around resonance frequencies delivered such parameters as elastic modulus and piezoelectric coefficients of InP, which could be compared with values from literature. The pertinent elastic modulus agrees within 1.6%, whereas the value of piezoelectric coefficient ∥e14∥=(1.3±20%) C/m2 is approximately three times higher than the older experimental value, but lies nearer to some theoretical predictions and to a recent experimental value.

Influence of deformation on the conductivity and photoconductivity of p-Type CdTe

Samples of p-type CdTe were subjected to deformation. Studies were performed of the influence of 60°-dislocations on the electrical conductivity, on the lifetime of minority carriers and on the relative change of the conductivity due to illumination.Dislocations were produced by bending the sample that was cut at suitable orientation. In this way, one obtained the 60°-dislocations, either of α- or β-type, according to the kind of bending involved.From the measurement of the temperature dependence of the conductivity it was ascertained that an increase in acceptor concentration occurs on the level with activation energy of 0.3 eV (identical to that of Vcd or a complex with Vcd), regardless of the type of dislocations. The concentration of acceptors on the level with activation energy 0.3 eV increases on increasing the dislocation density. The most probable explanation is that the deformation and, especially, annealinginduced migration of the dislocations produced give rise also to Vcd and/or VTe (both types simultaneously). Vcd acts as an acceptor and VTe as a donor. It follows that the increase in VTe can not be established from this measurement.The lifetime of the minority carriers is almost unaffected by introducing the dislocations into the samples. From the temperature dependence of the relative change in conductivity due to illumination one can determine the activation energy of a dislocation level provided that one assumes the dislocations acting as recombination centers. Under this assumption one obtainsEd=0.21–0.24 eV (for type α) andEd=0.55–0.59 eV (for type β), measured from the top of the valence band.

Fundamental extensional mode of circular quartz plates

The paper describes a new mode of vibrations found on. YΘ quartz plates which can be used for the control of oscillators. It is possible to find an orientation in which this mode has zero temperature coefficient of frequency.

Influence of annealing on the conductivity and photoconductivity of p-type CdTe

On annealing p-type CdTe, considerable change in conductivity takes place. Samples of high resistivity were used for the measurements. Each of a set of samples was annealed at different temperature. After annealing, the temperature dependence of the conductivity and the relaxation curves of the photoconductivity were measured. Analysis of the first set of curves yielded value of energyEa corresponding to the level occurring in given samples. It was established that this acceptor level is due to Vcd, or Vcd complexes, and is situated at 0.3 eV above the valence band edge. Concentration of these levels is increased by annealing. Furthermore, an energy value ofΔH=0.79 eV was found, corresponding very probably to the formation energy of a vacancy Vcd.Analysis of the relaxation curves yielded the temperature dependence ofτS,τT and the energy distanceEM of the impurity level that is responsible for photoconductivity. A value of (Eg-EM)=0.09–0.12 eV was found for all samples studied. This level therefore lies below the conduction band edge and its concentration amounts to 1014–1015 cm−3. The level is probably due to foreign impurities.Two sets of samples were used: both as-grown and Sb-doped. The results for both sets were not much different from each other.

Изучение крутилъных колебаний стержней э дт

AbstractПри изучении связей р азличных видов колеб аний анизотропных ма териалов исследовалисъ крути лъные колебания прям оуголъных стержней из ЭДТ, бырезанных из п ластинки по сечению Y п од различными наклонами к оси X. Была к ачественно проверен а правилъностъ теори и Фойта (Voigt) о связи между к олебаниями изгиба и к рутилъными колебани ями и установлено влияни е этой связи на такие р аэличные характерис тические признаки колебаний, к ак то: частоту, пъезоэл ектрическое возбужд ение и узловые линии.В этой работе впервые опубликованы резулъ таты измерений крутилъных колебани й анизотропных стерж ней с весъма разнообр азным положением сечения.