EFFECTS OF LOW-ENERGY ION EXPOSURE ON MODULATION-DOPED GAAS HETEROSTRUCTURES

in order to determine the electrical isolation mechanism of low energy ions impinging on GaAs heterostructures, a systematic magnetotranspor t study was performed on the two-dimensional electron gas (2DEG) of a GaAs modulation doped heterostructure. Sample devices were bombarded w ith 150 eV Ar+ ions while the room temperature resistances were measur ed in situ. The effectiveness of photoresist as a masking material was tested. Magnetotransport measurements were carried out in a dark cond ition at 4.2 K, and the resistance, mobility, and carrier density of t he 2DEG were monitored as functions of the ion exposure time. The isol ation results are consistent with a screening model for the 2DEG elect rons. In this model, the onset of electrical isolation is due to the b reakdown of the screening because milling of the surface results in de pletion of the 2DEG carriers. At present, no additional effects of the low energy ions, such as material damage from ion penetration, have b een confirmed