Models of column III and V elements on GaAs (110): Application to MBE

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Abstract
Models of ordered Sb overlayers on GaAs (110) are presented and discussed in terms of simple chemical considerations and the available data. The basic character (directional, covalent) of the Sb–GaAs bond is expected to apply to other column V elements on GaAs. Recent developments from theory in the understanding of column III metal–GaAs (110) bonding are summarized and compared to experimental data. It is proposed that the tendency for column III metals to bond nondirectionally on the (110) surface, while column V elements bond directionally, is highly relevant to molecular beam epitaxy (MBE) on all surfaces of III–V compounds. The basis of this proposal is the requirement that a column III atom must have several neighboring column V atoms before it can hybridize and form directional covalent bonds, while no such requirement of hybridization is necessary for the column V elements to bond to the surface directionally. One important result is that the column V element is initially responsible for establishing registry between the growing layer and (110) surface. For MBE on polar surfaces, column III adatoms are not expected to be stabilized in surface lattice sites without several neighboring column V elements.

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