Minority carrier lifetime in silicon wafers has been measured by applying an impedance spectroscopy technique (IST). Induced p + -p and p-n junctions were formed on both sides of the silicon wafer by thermally evaporating semitransparent metal layers of palladium and aluminium respectively. As such, no thermal treatment was given to the device, and therefore there is no diffusion of impurities inside the semiconductor and the two junctions are induced in the form of accumulation and depletion regions of charge carriers respectively. Both generation and recombination lifetimes applicable under the reverse and forward bias conditions respectively have been measured. The generation lifetime was estimated to be around 73 μs, whereas the recombination lifetime has been found to be about 11 μs. It is shown that the effective recombination lifetime is determined mainly by surface recombination velocity at the silicon-palladium interface. The effective minority carrier lifetime as measured by the microwave-detected photoconductive decay method on the same sample is 12 μs which is close to the measured recombination value by the IST. This shows that impedance spectroscopy can be used to measure effective lifetime of the wafer using an induced junction structure prior to the formation of an actual device like the solar cell. Moreover, the series resistance (R s ), diode ideality factor (n) and barrier height (V bi ) obtained from C-V (using the IST) data as well as the I-V measurement of the device show agreement with the expected device parameters. Thus, the IST can be effectively employed as a tool in extracting many relevant characteristic parameters of the material and the device.

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The Norde function [J. Appl. Phys. 50, 5052 (1979)] used for measuring the barrier height, series resistance, and ideality factor of a Schottky barrier diode has been modified to obtain the same parameters for a triangular barrier diode (TBD). Unlike Schottky barrier diodes, the barrier height of a TBD depends upon the applied voltage and changes linearly with it. In order to calculate the additive term in the TBD barrier height, the modified function is therefore plotted for both reverse and forward bias cases. It is shown later that the modified Norde function enhances the accuracy of the results.

Bulk barrier diodes are majority carrier diodes, in which the current is given by the thermionic emission of carriers over a barrier present in the bulk of the material. The height of this barrier depends on the dopings of the various layers of the diode, which has a p+np or n+pn structure. In this paper, different ways to determine this barrier height and its controlling parameters, have been suggested by considering the effect of temperature on the current and the applied voltage of the device.

Bulk unipolar diodes are majority-carrier three-layer (n-p-n) semiconductor diodes in which the current flows due to the thermionic emission of majority carriers over a barrier formed in the bulk of the material. Expressions for the barrier height of two typical bulk unipolar diodes, namely a bulk barrier diode (n++p+n) and a p-plane barrier diode (n+p++n), are derived. The functional dependence of the barrier height on various technological parameters is discussed. The two diodes are quite similar in their structure and characteristics. However, the p-plane barrier diode is more suitable as a majority-carrier diode. The variation of ideality factor and the saturation current of these diodes is shown to be very similar to the metal semiconductor diode.