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For the purpose of current leakage analysis in p/n junction narrow gap semiconductor diodes, the effect of hydrogen ion implantation and hydrogen plasma on InSb photovoltaic I-V diode characteristics was studied. The use of hydrogen discharge technique for semiconductor surface passivation just before or during the plasma CVD deposition of Si02 indicates that it is possible to obtain control of the flat band voltage parameter. Nevertheless, measurements of C-V hysteresis loops of MIS devices and I-V leakage measurements on diodes that had the same hydrogen passivation treatment as the MIS devices, do not show control of these parameters. For current leakage location identification we have carried out experiments with gate-controlled diodes (G.C.D) whose gate is located both on the mesa slope and at various distances from the slope, on both sides of the junction. In the electrical experiments with G.C.D, the device was operated either under external stress (compressive or tensile) or under stress-free conditions.
A quantitative model was developed for calculation of the current leakage, including the I-V gate- controlled diode characteristics. The model was based on an algebraic relationship between the gate voltage and the charge density near the oxide and the p/n junction and it has the potential to include different current leakage mechanisms. The model was confirmed experimentally, and an equivalent defect charge density in the layer between the oxide and the semiconductor, near the p/n junction, was obtained by analyzing either gate voltage or external stress. Using the parameters of gate voltage and external stress, we can induce various kinds of I-V leakage characteristics in a leak-free InSb diode, including negative resistance to forward bias. However, similar methods were not successful in inducing negative resistance characteristics in Hgl_x Cdx Te (MCT) photovoltaic p/n+ diodes. Deep energy-state density in the energy gap due to material defects or process-induced defects, may be responsible for the high excess currents observed. A discussion of the G.C.D.-induced current leakage characteristics as indicators for high quality substrate material in p/n diode fabrication is given.
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