Characterisation of dark current in novel Hg1-xCdxTe mid-wavelength infrared photovoltaic detectors based on n-on-p junctions formed by plasma-induced type conversion

This paper reports initial characterisation results for planar mid-waveleng th infrared (MWIR) photodiodes fabricated using a novel reactive ion plasma -induced n-on-p junction formation technology on vacancy-doped p-type HgCdT e grown by LPE on CdZnTe substrates. The junction is formed without the nee d for post-implant annealing typically required by ion implantation junctio n formation techniques to repair damage or to move the junction away from d amaged regions. The dark current and dynamic resistance, R-d, of the fabric ated photodiodes have been characterised as a function of temperature. At 8 0 K, the zero-bias dynamic resistance-junction area product (R(o)A) of the diodes is 4.6 x 10(7) Ohm cm(2), with the devices being diffusion limited d own to similar to 135 K. Dynamic resistance has been measured for temperatu res between 80 and 195 K and biases between - 200 and + 150 mV. Modelling o f the observed dark current has been undertaken using three distinct mechan isms, diffusion, generation-recombination, and tray-assisted tunnelling. Th e results show that the plasma-induced junction formation technique can pro duce high-performance planar HgCdTe photodiodes. The dark current mechanism s found in these devices are similar to those found in diodes formed using conventional ion implantation techniques. (C) 2000 Elsevier Science B.V. Al l rights reserved.