AS-4 PRESSURE-DEPENDENCE OF THE INTERFACE FLATNESS OF GAAS AL0.3GA0.7AS QUANTUM-WELLS GROWN ON (411)A GAAS SUBSTRATES BY MBE/

Arsenic pressure dependence of the interface flatness of GaAs/AlGaAs ( Al content of 0.27-0.29) quantum wells (QWs) grown on (411)A GaAs subs trates by molecular beam epitaxy (MBE) was investigated. Effectively a tomically flat (411)A interfaces could be realized under a low V/III r atio (V/III = 7), but the interfaces decreased in flatness under an in creased V/III ratio (V/III greater than or equal to 11), The linewidth of the photoluminescence peak increases with increasing the V/III rat io during the growth of the GaAs QW layers, but does not increase so m uch with increasing V/III ratio during the growth of the AlGaAs barrie r layers, indicating that the flatness of an AlGaAs/GaAs upper interfa ce of the GaAs QWs grown on (411)A substrates is more strongly affecte d by the high V/III ratio than that of a GaAs/AlGaAs lower interface o f the GaAs QWs. The excess fluctuation in the GaAs well width (Delta L -w) which results from the roughness of the upper interface caused by the high V/III ratio increases parabolically as a function of the GaAs well width (L-wo). This result was explained in terms of the formatio n of microsteps consisting of (311)A and (511)A microfacets on the ave raged (411)A GaAs surface. Sizes of the (311)A and (511)A microfacets increase in proportion with the GaAs well width (L-wo).