Yu. N. Purtov

Optical absorption and chromium diffusion in ZnSe single crystals

ZnSe:Cr single crystals were obtained using diffusion-related doping with chromium. The diffusion of chromium was performed in an atmosphere of saturated zinc vapors, and the metallic Cr layer deposited on the crystal surface was used as the source. Lines corresponding to chromium absorption at 2.766, 2.717, and 2.406 eV were observed in the optical-density spectrum at 77 K. The highest chromium concentration in the crystals was determined from infrared absorptance in the region of 0.72 eV and was found to be equal to 8 × 1019 cm−3. It is shown that the diffusion profile of the chromium impurity can be determined by measuring the optical density of the crystals in the visible region of the spectrum. The diffusion coefficients D of chromium in ZnSe crystals at temperatures of 1073–1273 K are calculated. An analysis of the temperature dependence D(T) made it possible to determine the coefficients in the Arrhenius equation: D0 = 4.7 × 1010 cm2/s and E = 4.45 eV.

Native and impurity defects in ZnSe:In single crystals prepared by free growth

The optical absorption and photoluminescence spectra and the Hall effect were studied in ZnSe:In single crystals. The presence of electrically active InZn+ donor centers responsible for the impurity absorption and electrical conduction of crystals is established. It is shown that the conduction compensation in the ZnSe:In crystals is effected by cationic vacancies. The InZn+ donors and cationic vacancies form associative defects responsible for long-wavelength ZnSe:In luminescence. A high crystal conductivity (∼5 Ω−1 cm−1) is achieved as a result of ZnSe:In annealing in the zinc melt, which results in the extraction of cationic vacancies. The electron mobility in high-conductivity crystals is limited by scattering at the LO phonons and macrodefects formed due to the reduction of In solubility in crystals by their annealing in zinc.

ZnSe blue-light-emitting diode

Abstract A zinc selenide p-n junction diode has been formed by Li thermal diffusion. Blue electroluminescence has been observed from this structure in forward bias at room temperature. The external quantum efficiency is about 0.5%.

Preparation and optical properties of Co-doped ZnSe single crystals

ZnSe single crystals doped via Co diffusion are investigated. The diffusion was carried out from metal Co in He or Ar atmosphere. The spectra of optical density in the wavelength range 0.4–2 μm are investigated. It is found that the absorption edge shifts as the concentration of doping impurities increases. This shift is caused by the formation of the Zn1 − xCoxSe alloy. The diffusion profile of the Co dopant is determined via measurement of the relative optical density of the crystals in the visible spectral region. The Co diffusivities (D) in the ZnSe crystals at T = 1103–1273 K are calculated. The analysis of the temperature dependence D(T) made it possible to determine the coefficients in the Arrhenius equation, namely, D0 = 3.4 × 106 cm2/s and E0 = 3.8 eV.

p-Type conductivity in ZnSe

Abstract Low-resistive p-ZnSe crystals can be obtained by heat treatment of as-grown specimens in molten Se and following by doping with Li. The properties of these crystals have been measured.

Indium doping of ZnSe single crystals during vapor phase growth

A process for indium doping of ZnSe single crystals during vapor phase growth is described. The solubility limit of indium in ZnSe is determined as a function of temperature and zinc selenide stoichiometry. The conclusion is drawn that the entire homogeneity range of ZnSe in the equilibrium phase diagram lies at selenium-enriched compositions.

Inversion of conductivity type in ZnSe single crystals obtained by the method of free growth

ZnSe:In and (ZnSe:In):Zn single crystals obtained by the method of free growth were studied. Inversion of the conductivity type was attained by annealing crystals in an atmosphere of saturated selenium vapors. Hole conductivity was attained for the first time in (ZnSe:In):Zn crystals with an initially high electron conductivity (3–5 Ω−1 cm−1). The origin of donor and acceptor centers responsible for the conductivity of crystals was ascertained.

Preparation and optical properties of the co-doped ZnTe single crystals

The ZnTe:Co single crystals are obtained by diffusion Co-doping. The spectra of optical density in the range of 2.4–0.38 eV are investigated. It is found that Co-doping of the crystals shifts the absorption edge to the low-energy region. The similarity of optical absorption spectra of the ZnTe:Co and ZnS:Co crystals is established. The observed absorption lines of ZnTe:Co are attributed to the optical transitions of electrons from the level of the ground state 4A2(F) of the Co2+ ion to the levels of excited states 4T1(P), 4T1(F), and 4T2(F) split by the spin-orbit interaction.

Luminescence of ZnS polycrystals prepared by SSHTS

The properties of hexagonal ZnS polycrystals prepared by the self-spreading high temperature synthesis have been investigated by the photoluminescence method. The comparison of poly- and mono-crystals emission properties were carried out. The effect of longtime luminescence relaxation in Cl- doped ZnS polycrystals was discovered.