A neutron activation technique has been used to analyze the gallium content in SiO2 films deposited on n-type GaAs. Gallium was observed in the SiO2 films after annealing at temperatures between 730 and 940 °C. It is found that the surface of GaAs reacts with the H2O in the SiO2 films and/or ambient gas via pinholes at these high temperatures. The reaction is influenced by the partial pressure of water in the ambient gas.
Articles you may be interested inHigh-tone bulk acoustic resonators on sapphire, crystal quartz, fused silica, and silicon substrates Diffusion ofGa into quartz (crystal Si0 2 ) and bulk-fused silica (amorphous Si0 2 ) was studied by neutron activation analysis. Slow and fast diffusion of Ga was observed in bulk-fused silica, while in quartz only slow diffusion was observed. The difference in the diffusion mechanisms is discussed on the basis of the difference in porosity of the two materials. In the bulk-fused silica, which has a lower density of2.20 g cm -3, there are two regions with high and low densities. The higher density region is composed of cristobalite, which has the maximum distance between atomic strings of (at most) 6 A. The lower density region is composed ofa random network ofSi and ° atoms, and in the network there exist many microchannels, an average diameter and the real density of which are estimated to be 17 A and 7.5 X lOll cm -2, respectively. These microchannels act as the high-speed diffusion paths, while the cristobalite region is the slow diffusion path. In quartz which has a density of2.65 g cm -3, the widest interatomic spacing perpendicular to c axis is about 5 A and only the slow (bulk) diffusion can occur. The discrepancy in the diffusion coefficients ofGa reported previously by Grove and Wagner can be explained by the present model.
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