Characterisation of dark current in novel Hg 1− xCd xTe mid-wavelength infrared photovoltaic detectors based on n-on-p junctions formed by plasma-induced type conversion

Abstract

This paper reports initial characterisation results for planar mid-wavelength infrared (MWIR) photodiodes fabricated using a novel reactive ion plasma-induced n-on-p junction formation technology on vacancy-doped p-type HgCdTe grown by LPE on CdZnTe substrates. The junction is formed without the need for post-implant annealing typically required by ion implantation junction formation techniques to repair damage or to move the junction away from damaged regions. The dark current and dynamic resistance, R d, of the fabricated photodiodes have been characterised as a function of temperature. At 80 K, the zero-bias dynamic resistance–junction area product ( R 0 A) of the diodes is 4.6×10 7 Ω cm 2, with the devices being diffusion limited down to ∼135 K. Dynamic resistance has been measured for temperatures between 80 and 195 K and biases between −200 and +150 mV. Modelling of the observed dark current has been undertaken using three distinct mechanisms, diffusion, generation–recombination, and trap-assisted tunnelling. The results show that the plasma-induced junction formation technique can produce high-performance planar HgCdTe photodiodes. The dark current mechanisms found in these devices are similar to those found in diodes formed using conventional ion implantation techniques.