Electrical properties of InP MIS devices

Abstract
Thin film metal-insulator-semiconductor devices have been prepared on n-type InP substrates. The metal used was aluminium and the insulating oxide film was produced using an anodisation technique. Diodes were made with oxide thicknesses of 40 AA and 110 AA and were evaluated using current-voltage measurements over the temperature range 150-350K and also capacitance-voltage techniques. Both sets of measurements were compared with current metal-insulator-semiconductor theory and values were obtained for the barrier height in the semiconductor. Reasonable agreement was found but an anomaly previously observed in the Richardson plot in Al-InP Schottky barriers was again evident in the devices. The capacitance-voltage results indicated a surface-state density in the region of 1012 cm-2 eV-1. Values were also obtained for the barrier height presented to electrons by the insulating layer. This proved to be rather smaller than expected, which suggests that the mechanism of current flow through the layer is not simple tunnelling.

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