武部敏彦
GaAsパターン基板上でのGaAsの
分子線エピタクシーにおけるGa表面拡散長の異方性
Abstract:Extra facet generation on ridge-type triangles with (001)-, (110)-, and (201)-related equivalent slopes on GaAs (111)A substrates and stripes running in the
[110], [110], and [100] directions on (001) substrates during molecular beam
epitaxy of GaAs/AlGaAs multilayers was investigated. Growth of extra (114)A,
(110), and (111)B facets was common to the (111)A and (001) patterned
substrates. By investigating local variation in layer thickness in the regions
adjacent to these facets and extra facets specific to the respective substrates, the
orientation-dependent Ga surface diffusion length,λGa, was elucidated asλGa(001)
～λGa(113)B < ｛λGa(111)B, λGa(331)B, λGa(013),
λGa(113)A}＜λGa(159) ～
λGa(114)A～ λGa(111)A ≦λGa(110)．
Considering application of patterned substrates to the fabrication of lateral p-n
junctions, the present result that λGa(001) is the shortest may limit the use of
(001) substrates because an exponential variation of the layer thickness always
appears on the (001) substrate plane at the boundary with the sidewall and
hampers the formation of simple structures. In contrast, (111)A and (110)
substrates with relatively long λGa are free from such a limitation, and hence may be more suitable for such applications, although epitaxial growth of good layers on (111)A and (110) surfaces is very difficult. On the other hand, the (001) substrate will be suitable for the formation of quantum wires and dots on
patterns with dimensions around λGa because the preferential incorporation of Ga
adatoms into the (001) surface leads to enhancement of the growth rate in the
(001) direction and suppression of the growth rates in the other directions.
Key words : gallium arsenide, aluminum gallium arsenide, patterned substrate,
molecular beam epitaxy, crystal facet, diffusion length.