M. Zvára

Preparation and basic physical properties of single crystals of cadmium chromium selenide CdCr2Se4

Single crystals of CdCr2Se4 were prepared by crystallization of polycrystalline material from the melt of cadmium chloride and by synthesis from anhydrous CrCl3 and CdSe. Basic optical and transport properties were measured on the crystals. The results are compared with the available literature data and a brief survey of existing interpretation is given.

Interface trap conductance spectroscopy of a narrow-gap Hg1-xCdxTe (x approximately=0.2) MIS device

The observation of a pronounced double peak structure in the equivalent parallel conductance of a metal-insulator-semiconductor (MIS) device prepared on a Bridgman-grown x approximately=0.2 p-type Hg1-xCdxTe crystal passivated by an anodic oxide layer is reported. The first peak, placed in the depletion part of the conductance-voltage (G-V) curves, has been attributed to the response of single-level interface traps distributed over the semiconductor gap supposing band-bending fluctuations. The second peak, placed at the onset of strong inversion, is due to shunting of the minority carrier flow by the electrons coming from the inverted surface area beyond the gate. An order of magnitude enhancement of the structure measured on capacitance-voltage (C-V) and G-V curves below T approximately=10 K has been attributed to hole freezeout, leading to a substantially slower sample response and to an exponential increase of its series resistance. The tunnelling from acceptor states near the Fermi level to interface traps and/or to light hole states in the valence band becomes a competing mechanism to majority carrier response in the depletion and accumulation regions in that case.

THE ABSORPTION EDGE IN P-TYPE HG1-XCDXTE (X 0.2)

Abstract The optical absorption edge of the low concentration p-type single crystals Hg 1− x Cd x Te with composition x ∼ 0.2 was investigated in the temperature range from 5 K to 300 K. The shape of the absorption edge depends strongly on the quality of the crystals. For the high-quality samples, two contributions with different slopes and with different temperature evolutions are resolved on the absorption curve.

111In(111Cd) quadrupole interaction in the chalcogenide spinel CdCr2Se4

The111Cd quadrupole coupling in the spinel CdCr2Se4 is investigated by TDPAC after different sample treatments. The experiments are consistent with Se vacancies causing the non-cubic probe environments and with the assumption that the majority of the111In atoms are positioned at A-sites.

Magneto-conductance spectroscopy of a narrow-gap MIS device

The equivalent parallel capacitance and conductance of a metal - insulator - semiconductor (MIS) device prepared on low-concentration p-type exhibit, in an external magnetic field, well-resolved oscillations both as a function of gate voltage and magnetic field B, when biased into inversion. The oscillations result from a magnetic-field-induced modulation of the two-dimensional (2D) density of states (Landau levels) either in the inversion layer developed under the MIS gate contact (when measured at fixed B) or in the inverted surface under the passivating anodic oxide layer in the area surrounding the gate (when measured as a function of B with kept constant). The minority carrier transport mechanism is discussed and by using Fourier analysis of the observed oscillations, the number and partial occupancies of the 2D quantized subbands of the inverted surface layer are deduced. The shallow acceptor activation energy meV is evaluated from the observed carrier freeze-out.

FT-IR spectroscopy of magneto-optical oscillations in Hg1−xCdxTe photodiodes

Interband magneto-optical transitions in Hg1−xCdxTe implanted photodiodes were investigated by utilizing FT-IR spectroscopy. A typical pattern of Landau level transitions was observed in photovoltaic spectra of the diodes. Moreover, a structure resembling transitions to localized states was indicated on several samples.