The bound exciton spectra of ZnSe crystals at 4.2 °K were measured following the heat treatment of the samples in Zn or Se. As a result of Se treatment only the I1 line with the binding energy 19 meV is observed, whereas after Zn treatment a new I*2 line with the binding energy 2 meV appears. These final states are reversible and the lines are ascribed to the intrinsic defects V Zn× and V Se×, respectively.

Below-gap structures in photoreflectance spectra of semi-insulating GaAs were observed originating from electroabsorption of light reflected from the back surface. The peak amplitude of these structures was strongly temperature dependent within the range (78-290) K. The different lineshape at low temperature in comparison to that at room temperature suggested different physical mechanisms. This conclusion was proven experimentally using a two phase lock-in technique by which a fast (3 and slsw (Yj component of the spectra could be separated. A fit procedure provides the pure back surface reflection effect for both components. The X mode dominating at low temperatures is attributed to electromodulation of the field-broadened excitor& absorption tail whereas the Y mode originates from the Franz-Keldysh electroabsorption.

The properties of the n-St electrode in both aqueous and organic solution for nonstabilizing conditions were studied by the electrorefleetance and capacitance techniques. A shift of the flatband potential in the anodic direction up to 0 VseE has been observed for both solutions and was more pronounced for the aqueous one. The strong influence of polarization under anodic potentials on the properties of the St/electrolyte junction is shown. It is demonstrated that the flatband potential shifts for solutions without a stabilizing agent is caused by the slow oxidation process and related interface state evolution. Anomalously high electroreflectanee signals have been observed for the potentials where a capacitance peak associated with the interface states is detected. We suppose the interaction of hydrogen-related species in a subsurface Si layer with interface states to be responsible for this specific electrorefleetance modulation.

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An investigation is made of the recharging processes of ions of chromium inserted by substitution on zinc sites in ZnSe single crystals. Opposed are corresponding spectra of the photoconductivity against spectra of excitation and quenching of the Cr+ ‐EPR signal. Supplementary statements are obtained from optical and electrical measurements. With the exception of the optical ionization of the Cr+ ‐centres three typical mechanisms of recharging are confirmed by the measurements. The energy of the unoccupied Cr|Zn|′ ‐term is determined to 2.45 eV above the top of valence band. For the occupied Cr|Zn|′ ‐term it is found, that the corresponding energy exceeds not a maximum distance of 0.9 eV below the conduction band edge.