SELECTIVE-AREA GROWTH OF GAAS USING A GA BEAM WITH A STEP-FUNCTION LATERAL INTENSITY PROFILE

Selective area growth of GaAs has been carried out in order to investi gate the surface diffusion of Ga atoms using molecular beam epitaxy (M BE) with the aid of a Ga beam with a lateral step-function intensity p rofile. This step-function profile was obtained using a closely fitted GaAs shadow mask. When the mask edge was parallel to [01 $$($) over b ar 1], a (311)A facet was typically observed near the edge of the Ga b eam, while in the case of the mask edge parallel to [011], a (111)B fa cet was formed. MBE growth simulation based on the diffusion model was carried out in order to understand the mechanism of this selective ar ea growth. The calculated results were in good agreement with the expe rimental results, and the diffusion lengths of Ga atoms were determine d to be 0.10 mu m along [011] direction on the (100) GaAs surface, 0.3 7 mu m along [233] direction on the (311)A GaAs surface and 0.17 mu m along [21 $$($) over bar 1] direction on the (111)B GaAs surface durin g MBE growth. These diffusion lengths seem to be smaller than those pr eviously observed, which is probably due to a large V/III ratio in the region of the substrate close to the mask edge.