Abstract
The regrowth of (AlGa)As over substrates patterned in 〈0 1 1〉 directions is an important step in the fabrication of index-guided laser structures. We present a detailed study of the influences of growth parameters on the development of the regrowth front and the composition profile. The overgrown (AlGa)As exhibits an inhomogeneous Al profile, strongly dependent on growth temperature, with less Al on the {3 1 1} -sidewalls of the trenches than on planar facets. The ratio of the growth rate on the sidewalls to the planar growth rate is used to characterize the development of the growth front, and its dependence on reactor pressure, growth temperature and trench orientation is studied. Differences in the growth behavior for the two trench orientations are found with overgrowth on [0 1 ̄ 1] trenches being very sensitive to V/III ratio. This allows an estimation of the efficiency of the As precursors arsine (AsH 3) and tertiary butyl arsine (TBAs) with TBAs being seven times more effective than AsH 3 at 600°C. The observed growth behavior is discussed in terms of group III mobilities, diffusion processes and bonding situations on the different surfaces.
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