A.S. Nasibov

Vapour growth and characterization of bulk ZnSe single crystals

Large (up to 60 mm in diameter) untwinned ZnSe single crystals have been grown in sealed quartz ampoules by seeded physical vapour transport and seeded chemical vapour transport with hydrogen. The dependence of structure perfection on the seed quality and its orientation, the source design, the gas filling of the growth ampoule and the temperature regime was researched. Selective chemical etching topography, X-ray diffraction rocking curve and cathodoluminescence studies are presented to characterize grown crystals. The influence of oxygen impurity on crystal emission and weakening of this influence in crystals grown in hydrogen was found. The results of crystal annealing in Zn vapour and Zn melt are discussed.

Exciton luminescence in ideal solid solutions (ZnxCd1−xSe system,0 < x < 1)

The temperature and concentration dependences of exciton emission spectra in ZnxCd1−xSe solid solutions (0 < x < 1) have been studied. It has been shown: (1) high efficiency of the luminescence of localized exciton states (LES) produced by large-scale potential fluctuations, (2) absence of the energy gap between LES and exciton band bottom states. Results obtained have common meaning for ideal solid solutions, in which distribution of substitutional atoms is random.

Vapour growth and doping of ZnSe single crystals

The results of seeded vapour-phase free growth of ZnSe single crystals in both the and directions are presented and discussed. Optimum growth conditions were found to be essentially different for these two directions. The doping by In and Al from both vapour phase during the growth process at T = 1180-1240°C and liquid phase by means of annealing in liquid Zn with In or Al additions at T = 900-950°C was performed. To characterize grown crystals, selective chemical etching. X-ray diffraction rocking curve, cathodoluminescence study, atomic-emission analysis, specific resistance and Hall effect measurements were carried out.

Seeded vapour-phase free growth of ZnSe single crystals in the 〈1 0 0〉 direction

Abstract Seeded vapour-phase free growth of ZnSe single crystals at T g = 1100–1250°C in 〈1 0 0〉 direction was studied. The 〈1 0 0〉 growth process was found to be more sensitive to the temperature profile in a furnace than the 〈1 1 1〉 direction. The problem that seed attachment to a support pedestal is followed by a generation of high dislocation density was solved by use of a reverse temperature gradient along the axis of the furnace between the seed and the pedestal and by optical monitoring of the attachment process during the growth. Seeds with dislocation density of 10 4 –10 5 cm −2 and 2–4 cm 2 area selected from single crystals grown in 〈1 1 1〉 direction were used for the first growth processes in 〈1 0 0〉 direction. To increase the diameter of the grown crystals, a tangential growth regime was developed. Twin free ZnSe single crystals of 51 mm diameter and of 15 mm height were grown in helium. The average dislocation density was about 10 4 cm −2 and the full-width at half-maximum (FWHM) of the X-ray rocking curve was as small as 16 arcsec.

Vapour phase and liquid phase doping of ZnSe by group III elements

Abstract A vapour phase doping of ZnSe single crystals by In impurity during a growth process at T = 1180°C was developed. A liquid phase doping was performed by means of annealing of crystal wafers in liquid Zn with an addition of In or Al at T = 900°C. Atomic-emission analysis, cathodoluminescence study, specific resistance and Hall measurements were carried out. The concentration of the In and Al impurities in ZnSe single crystals were in a range from 10 17 to 10 19 cm −3 . High n-type conductivity in the ZnSe single crystals doped by In or Al impurities was achieved: the specific resistance was as low as 0.05 Ω cm for the Al liquid phase doping and about 1 Ω cm for the In vapour phase doping followed by annealing in the liquid Zn : In.

Resonant brillouin scattering from polaritons in ZnSe/GaAs epitaxial layers

Abstract The first observation of resonant Brillouin scattering in an epitaxially grown semiconductor layer is reported. The material is ZnSe grown by metalorganic vapor phase epitaxy on a GaAs substrate. We have studied the spectra and kinetics of the emission occurring under resonant optical excitation in the exciton-polariton region by a tunable picosecond laser. The Brillouin scattering data are used to analyze in detail the effect of strain in the sample and determine the exchange splitting of the exciton states, which is found in quantitative agreement with the reflectivity.

Spectroscopic investigations of semiconductor solid solutions with structural phase transition (ZnxCd1-txSe system)

Abstract Low temperature (T = 2 K) spectra features of exciton reflection and luminescence of monocrystals of semiconductor solid solutions ZnxCd1−xSe with structural phase transition have been investigated.

Solid II–VI Solutions as active media for a laser electron-beam-tube

The properties of laser electron-beam-tube (LEBT) laser elements based on solid solutions of II-VI semiconductor compounds are presented. The fundamental absorption edges of these compounds are investigated. Their radiative properties are analyzed. A correlation is found between the emissivities of solid solutions, the characteristics of their fundamental absorption, and the results of investigations of laser elements based on these compounds. It is shown that Zn1−xCdxS and Zn1−xSe are promising solid solutions for use in LEBT operating at T>80 K, while CdS1−xSex and ZnS1−xSex are promising at T<150 K.