P 2-induced [formula omitted] exchange on GaAs during gas-source molecular beam epitaxy growth interruptions

Abstract

P As exchange behavior on GaAs under a P 2 flux in a gas-source molecular beam epitaxy (GSMBE) system has been studied by reflection high-energy electron diffraction (RHEED), high-resolution double-crystal X-ray rocking curves (DCXRC) and cross-sectional scanning tunneling microscopy (STM). We found that the exposure of GaAs to a P 2 flux results in severe substitution of As atoms by P atoms at the normal temperature for growing GaAs ( T s = 570°C). When T s < 500°C, a streaky RHEED pattern can be maintained even during P 2 flux exposure of over 10 min. DCXRC of a 25-period P 2-exposed GaAs structure grown at 550°C show a set of satellite peaks, indicating formation of a periodic structure. Approximately an average of 0.45 monolayer of phosphorus is incorporated at each interface via As P exchange. High-resolution cross-sectional STM images reveal non-uniform (both laterally and vertically) interfacial layers of width as large as 10 monolayers. For the sample grown at 450°C, no clear satellite peaks are present. STM images of the sample exhibit much thinner interlayers, consistent with a lower level of phosphorus substitution.