By in-situ surface photo-absorption (SPA) monitoring of MOVPE grown GaAs(111)B surface, three types of surface phases, (2×2)-like, (√19×√19)-like, and (1×1)HT-like, are identified. Eight-μm-wide atomically step-free surfaces and interfaces are successfully obtained by controlling the surface phase and by using finite area epitaxial (FAE) growth. Their flatness is confirmed by ex-situ AFM and low-temperature (4K) spatially resolved photoluminescence (SR-PL) measurement. A flattening principle of FAE is discussed, where two-dimensional (2D) nucleation is suppressed on GaAs(111)B surface due to desorption and surface migration. It is concluded that, by utilizing desorption, a step-free surface of any size can be formed as long as the size is finite. To demonstrate this, an extraordinarily wide step-free GaAs(111)B surfaces 100μm in diameter are successfully formed. Surface stoichiometry control based on insitu SPA monitoring is indispensable for flatness control.
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