Generation-recombination effects in high temperature HgCdTe heterostructure photodiodes

The effect of built-in electric fields and misfit dislocations on dark currents in high temperature, MOCVD HgCdTe infrared heterostructure photodiodes has been investigated. From experimental data results that the current-voltage characteristics at 240 K and 300 K indicate significant contributions from tunnelling effects. which dominate file leakage current mechanism for reverse bias greater than a few tens of milivolts. Standard theoretical models show that Auger generation-recombination processes determine dark current in high temperature HgCdTe, photodiodes. But faking into account only Auger mechanisms much overestimated theoretical results air obtained. To explain this fact. a two-dimensional model has been developed to investigate the dark current mechanisms in the vicinity of the junction termination at built-in electric fields. files of the energy bands and electric field along different cross-sections of the photodiode indicate that the electric-field achieves a maximum value of the order of mid 10(5) V/cm in the area the junction termination at the HgCdTe heterointerface . In these region the high density of misfit dislocations are observed too. The presence of high electric field in this area decreases file regions the high density ionisation energies of trap levels located in region of dislocations core, and hence increases file efficiency of Shockley-Read-Hall generation-recombination process. In addition to diffusion, generation-recombination and trap assisted tunnelling mechanisms, our model include the Poole-Frankel and phonon-trap assisted tunnelling effects in calculations of dynamic resistance of the junctions. The best fit of experimental data with theoretical predictions for dynamic resistance versus temperature has been obtained for dislocation density in the bulk of HgCdTe layer equal to 5 x 10(-7) cm(-2).