Analyse de la decroissance du photo-courant dans Hg 0.7Cd 0.3Te entre 4,2 et 300k

Abstract

Photoconductive properties of Hg 0.7Cd 0.3Te have been studied in the temperature range 4.2–300K. A maximum and a minimum are found respectively at T ∼ 170K and T = 50K in the curve corresponding to the measurement of the photocurrent versus T. We also report the curves of the excess photocreated carriers density ( n e versus the light excitation. The decrease of this excess carriers density with time shows a lot of recombination mechanisms. In the temperature range 300-140K, the recombination process is only due to a radiative recombination. When T < 140K, two stages, with various lifetimes, take place in the decrease of n e : first lifetime, fast (<1μs) corresponds also to the band-band radiative recombination: the second lifetime, which increases as T decreases, corresponds to a recombination on deep acceptor centers. Finally, for T < 15K and if the excitation is not too weak, the recombination occurs on shallow acceptor centers; this leads up to a very high lifetime (∼ 300 μs), lifetime really related to the small capture sections for the electrons.