DARK CURRENT ANALYSIS OF SWIR HGCDTE PHOTOVOLTAIC DETECTORS

An investigation has been made of the dark current mechanisms Of SWIR (2-3 mum) HgCdTe photovoltaic detectors fabricated for optical fibre c ommunication applications. The photodiode forward and reverse current- voltage (I-V) characteristics, as well as the temperature dependence o f the zero-bias dynamic resistance (R0), were measured in the temperat ure range of 78-300 K. A qualitative analysis of experimental results was carried out using relevant theories. It is found that the diode pe rformance is mainly limited by surface channel leakage current origina ting from the p-side surface. Moreover, various current components flo wing through the field-induced junction may make contributions to surf ace channel current and dominate in different temperature and bias reg ions. In the high- and intermediate-temperature regions, diffusion and generation-recombination current, respectively, take a dominant role. In the low-temperature region, the reverse bias characteristics are g overned by some soft leakage current component, while the near zero an d forward bias characteristics have the features of deep level-assiste d tunnelling current. The reverse breakdown voltage of the bulk p-n ju nction is governed by an avalanche breakdown mechanism at low temperat ures and by a thermal breakdown mechanism at high temperatures.