Characterisation of dark current in novel Hg_(1-x)Cd_xTe mid-wavelength infrared photovoltaic detectors based on n-on-p junctions formed by plasma-induced type conversion

摘要

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_0A) of the diodes is 4.6 x 10~7 Ωm~2, with the devices being diffusion limited down to ～135K. Dynamic resistance has been measured for temperatures between 80 and 195 K and biases between -200 and + 150mV. 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.