InSb Photodiodes (Review. Part V)

Abstract

The results of research on the recombination of non-equilibrium charge carriers in n-InSb single crystals are analyzed. It is shown that the Shockley-Reed-Hall recombination models described in the literature are unable to explain the experimental results obtained in single crystals of applied quality, which are used to create infrared photodiodes. The proposed model of recombination with the participation of two independent levels, one of which is an acceptor. The model is based on the results of experimental studies of the lifetime in n-type InSb obtained from measurements of photoconductivity relaxation under pulsed laser excitation in the temperature range of 77-250 K. For the measurements, n-type conductivity single crystals grown by Czochralski method and obtained from several sources were used. The concentration of charge carriers in the samples at a temperature of 77 K varied within 1014-1016 cm-3. The kinetics of photoconductivity was studied in n-InSb samples before and after the formation of diffused p+-n junctions. The diffusion temperature of the cadmium acceptor impurity varied between 380 and 420 0С. It is shown that in the samples after the formation of the p-n junction, the lifetime can be limited by the effect of the trapping of minority carriers to the acceptor level, which is located at a distance of 60 meV from the bottom of the conduction band. The model allows describing the dependence of lifetime on temperature and carrier concentration in the doping range of 1014 - 1016 cm-3. From the comparison of stationary and transient lifetime, conclusions are drawn regarding the existence of the effect of the trapping of minority carriers in the material of n-type conductivity, which is responsible for the excess tunnel current in photodiodes, generation-recombination and low-frequency 1/f noise. It is assumed that acceptor traps can be caused by the generation of dislocations during the formation of a diffused junction.