Patterned growth on GaAs (311)A substrates:: Dependence on mesa misalignment and sidewall slope and its application to coupled wire-dot arrays

During molecular beam epitaxy of (AlGa)As on patterned GaAs (311)A substrates, mesa stripes along [01-1] develop a fast- growing sidewall with a smooth, unfacetted, convex surface profile which has been utilized for the formation of lateral quantum wires. In the present study this growth mechanism is found to be strongly sensitive, both on the misalignment of the mesa stripes from the [01-1] direction as well as on the sidewall slope. For wet chemical etching which produces a 50 degrees steep sidewall of the starting mesa stripe along [01-1], the formation of the convex surface profile is not affected for a misalignment smaller than 20 degrees. Above 20 degrees, the selectivity of growth monotonically decreases and the surface profile continuously develops into that of the slow growing concave sidewall along the perpendicular [-233] direction for misalignment larger than 50 degrees. In contrast, for reactive ion etched vertical sidewalls, almost no growth occurs for [01-1]-oriented mesa stripes while the evolution of the fast growing sidewall is recovered for misaligned mesa stripes. This behavior, which is qualitatively related to the bond configuration of the starting side facets, thus provides a unique parameter to control the selectivity of growth on patterned GaAs (311)A substrates, which is utilized for the formation of coupled wire-dot structures. (C) 1999 American Institute of Physics. [S0021-8979(99)00607-6].