In a modified metalorganic chemical vapor deposition, flow-rate modulation epitaxy, the growth rate of GaAs can be higher than one monolayer per cycle (0.28 nm/cycle). Ga-atoms, the number of which is up to 3 times as high as the surface site number, and arsenic are alternately supplied on the (001) GaAs substrates to grow GaAs layers. There is no surface degradation of the epitaxial layers even at a growth rate of three monolayers per cycle. In this method after Ga-atomic layers are formed, As atoms diffuse into the Ga-atomic layers to form a GaAs single crystal. In GaAs layers grown under such conditions, the concentration of the midgap level, “EL2, ” is much reduced. Furthermore, photoluminescence measurement indicates that high-quality GaAs layers are grown.
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