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GaAs field emission cathodes giving symmetric and reproducible emission patterns were prepared by chemical etching and low-temperature field desorption. Both electron and hydrogen ion images were obtained, although the latter showed little detail since field etching was rapid in the presence of hydrogen. Distinct differences were observed in the emission patterns and surface behavior between tips oriented in the 111 direction and tips oriented in the 1̄1̄1̄ direction. Surface migration of both Ga and GaAs was more rapid on the (1̄1̄1̄) B or As face which became thermally disordered above 300°C. The (111) A face remained ordered up to 400°C. On both faces adsorbed Ga decreased the work function by ∼0.5 V while adsorbed As reduced the emitting area without altering the work function appreciably. Heating the emitters above 500°C permanently altered the emission characteristics which then became strongly light sensitive. This was evidently due to doping changes by impurity diffusion.
John R. Arthur (1966) studied this question.