Facet generation during molecular beam epitaxy of GaAs/AlGaAs multilayers on GaAs(111)A patterned substrates

Extra facet generation during molecular beam epitaxy of GaAs/AlGaAs multilayers on exact (111)A GaAs substrates patterned with ridge-type triangles with (001)-related, (110)-related, and (201)-related sidewalls, designated as ''(001) triangle'', ''(110) triangle'', and ''(201) triangle'', respectively, has been investigated for the first time. Extra <((11)overbar 3)>A, (001), and (114)A facets have been generated on the (001)-related sidewalls, extra <(11(1)overbar)>B, (110), and (113)A facets on the (110)-related sidewalls, and extra <((1)overbar 01)>, <((2)overbar 38)>, <((1)overbar 25)>, and (159) facets on the (201)-related sidewalls, depending on the intersection angle 8 of the sidewall and the substrate plane. Of these, the (114)A, (110), and (159) facets were important because they persisted over a wide range of theta and, therefore, played a detrimental role in forming flat and uniform sidewall layers on the (111)A patterned substrates. The (110) and (NNM)A (N = 2, 3,...; M less than or equal to N - 1) facets developed on the corners of the (001) and (201) triangles, while no extra facets developed on the corners of the (110) triangles. It has been made clear that flat and uniform layers maintaining the initial as-etched triangle patterns can be grown without generating any extra facets on the sidewalls or corners for the (001) triangles with 33 degrees greater than or equal to theta greater than or equal to 29 degrees, the (110) triangles with 30 degrees greater than or equal to theta <greater than or equal to 16 degrees, and the (201) triangles with 33 degrees greater than or equal to theta greater than or equal to 26 degrees.