Laser-induced structure defects and their use for (Cd,Hg)Te epitaxial layers and CdTe crystals properties modification

Abstract

The work deals with the experimental researches of the processes of structural defects generation in (Cd,Hg)Te epitaxial layers on the CdTe substrates and CdTe monocrystals after impulsive laser processing and their influence on the mechanical, optical and galvanomagnetical properties. In the experiments we used the ruby laser radiation with energy density, changed in the range of 1,5-15 J/sq.cm. The duration of the laser impulses was about 1,5 ms and 20 ns. Changes in the chemical composition of the irradiated surface have been analyzed by Auger electron spectroscopy. The zones with increased defects concentration were determined by the method of selective chemical etching. It was shown, that the impulsive laser processing results in both the essential redistribution of the components concentration and generation of the linear and dot defects in the near-surface crystal layers, excited by the laser irradiation. Microhardness of the surface, irradiated with the laser without preliminary heating increases in the average on 20-30%. The photoluminescent properties of the laser modified cadmium-telluride samples were investigated in the spectral range of 650-1000 nm. After the laser irradiation of the samples the redistribution of the intensity of the luminescence bands and emergence of new band was observed in the region of 840 nm, when the temperature of samples was about 4,2 K. The essential growth of the spectral band intensity with a maximum within the range of 875-885 nm, when T= 77 K, was observed as well. Diminution of the life time of non-equilibrium charge carriers in a defective zone creates the premises to the magnetoconcentration effect origin in the crossed electrical and magnetic fields. The perspective of usage of such (Cd,Hg)Te structures as infrared and magnetic field sensors is shown.