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.
We have investigated the effect of selenium treatment of GaAs on the metal-insulator-semiconductor (MIS) Schottky diode characteristics. The resuits show that the surface-state density and trap density at the interface decrease. This resu!'; in decrease in the harrier height and retierse cwe.!. The treated diodes showed little aging effect. These observations can be explained using t h e formation of arsenic-selenium and selenium-selenium bonds at the surface and in the thin layer next to the surface within the GaAs.
The effects of rapid thermal annealing on t h e electrical characteristics of Ni and Pd contacts on n-lnP are investigated. Results show that annealing at temperatures up to 450 ' C and for durations u p to 100 s has little effect on the electrical parameters of these contacts. Contacts annealed at 600 "C showed some degradation. Contacts annealed at 450 "C and 600 ' C for 100 s showed an aging effect. Different reaction processes at the interface and formation of an InP surface layer with no stoichiometry are used to explain the observations.
The value of experimental Richardson constant (A*) is found to be a function of metal film thickness, type of the metal, method of deposition, and condition of semiconductor prior to metal deposition. In the case of Al and W on GaAs, the value of A* is found higher than the theoretical value. However, as the film thickness increases, the value of A* decreases. The larger value of A* is related to electrically active defects at the interface produced during sputtering. Filament evaporation results in smaller values for A*. In the case of WSi0.6 the presence of Si affects the value of A*. For InP, the value of A* is found smaller than the theoretical value. For both GaAs and InP, the value of A* increases when the semiconductor is annealed prior to metal deposition. This increase is significant in the case of InP.
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