Electrical studies on ion-etched n-GaAs(100) surfaces
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The major objective of this thesis was to evaluate electrically the damage caused by a low energy (< 4keV) Ar+ bombardment on n-GaAs(100) surfaces. Electrical measurements were performed on Schottlky diodes formed on the virgin and the ion-etched surfaces.
The l-V measurements show deterioration of diode parameters by ion etching. The ion etched diodes have a strong component of surface leakage current. The high frequency capacitance of ion-etched diodes is less than that of the virgin diodes. The low frequency capacitance of ion-etched diodes was found to be frequency dispersive. The extent of frequency dispersion diminishes at low temperatures and at low reverse biases. Virgin diode capacitance, on the other hand, was found to be independent of frequency.
The electrical characteristics of ion-etched diodes are explained by means of an amorphous layer and a donor-like damaged layer formed as a result of ion etching. The depth of the top amorphous layer increases with etch energy. The damaged layer containing the ion induced traps superimposes over the amorphous layer and extends deep into the bulk semi-conductor. The density of such traps is very bias sensitive and also temperature dependent.
A possible equivalent circuit model for the ion-etched material is proposed. Low temperature isochronal annealing (< 450Â°C, 10mins.) was not found effective in causing complete recovery of the ion-damaged surface.
- Masters Theses