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We have studied the photoresponse ͑transmission and photoconductivity of Corbino-shaped devices͒ of structures with InSb quantum wells ͑AlInSb barriers͒. To characterize the devices, the Shubnikov-de Haas ͑SdH͒ effect up to magnetic fields B of 7 T and current-voltage ͑I-V͒ characteristics at various magnetic fields were measured. Some of the samples showed clearly resolvable SdH oscillations. The I-V curves showed pronounced nonlinearities. The phototransmission and the photoconductivity at various terahertz ͑THz͒ frequencies were measured around 2.5 THz generated by a p-Ge laser. From the cyclotron resonance ͑transmis-sion measurements͒ we deduced a cyclotron mass of 0.022m 0 . We also performed photoconductivity measurements on Corbino-shaped devices in the THz frequency range. Oscillations of the photoconductivity with maxima near the minima of the conductivity in the dark were observed. Thus, these devices are potentially suitable for the detection of THz radiation.

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Post-grown annealing of (211) (CdZn)Te substrates has been used for elimination of Te and Cd inclusions with the objective of improving the yield of inclusion-free substrates for MBE growth of (HgCd)Te. Different annealing temperatures and Cd/Te overpressures were used to find the optimum annealing conditions. Te inclusions were significantly reduced by Cd-rich annealing at temperatures higher than 660°C, together with increasing the infrared transmittance at 10 lm to above 60%. Good crystalline quality was preserved after the annealing. Te-rich annealing at 700°C was found to be the optimum method for elimination of most of the Cd inclusions; infrared transmittance at 10 lm was suppressed by the annealing, however. Final Cd-rich annealing is recommended for infrared transmittance improvement.

The optical absorption edge of bulk CdTe single crystal was measured by infrared transmission under saturated Cd pressure in the temperature interval 295–1223 K. The absorption coefficient was directly determined up to the value of 100 cm−1. For higher values, it was estimated by extrapolating the spectra according to the Urbach exponential rule. It was observed that the common temperature-independent intersection of extrapolated Urbach absorption edge, the “Urbach focus,” does not exist in CdTe. The temperature dependence of band-gap energy Eg defined by Eg(300 K) = 1.518 eV and dEg/dT = − 4.4 × 10−4 eV/K was established, postulating linear temperature dependence of Eg by fitting the temperature dependent absorption coefficient at the band edge αg(T) = 6600 – 4T (K) (cm−1).

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CdZn)Te with the composition of 3% Zn and In-doped CdTe single crystals were annealed at various annealing temperatures and under various Cd or Te pressures with the aim of eliminating Te or Cd inclusions. Te inclusions were reduced by Cd-saturated annealing at temperatures above 660°C. Only small (<1 lm) residual dark spots, located at the original position of as-grown inclusions, were observed after annealing. The size of Cd inclusions was reduced by Te-rich annealing at temperatures higher than 700°C. A specific cooling regime was used to eliminate new small Te precipitates ($1 lm) concurrently formed on dislocations during Te-rich annealing. Poor infrared transmittance of samples with Cd inclusions was detected after Te-rich annealing; therefore, Cd-saturated re-annealing of annealed samples was used for increasing infrared transmittance to a value above 60%. Alternative models explaining the formation of star-shaped corona-surrounding inclusions are discussed.