Oxygen incorporation into MBE-grown AlGaAs layers
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Oxygen incorporation into MBE-grown AlGaAs layers S. Naritsuka, O. Kobayashi, K. Mitsuda, T. Maruyama and T. Nishinaga* Materials Science and Engineering, Meijo University, 1-501 Shiogama-guchi Tenpaku-ku, Nagoya 468-8502, Japan *Present address: Toyohashi University of Technology, Toyohashi, Aichi 441-8580 Japan ABSTRACT The incorporation mechanism of oxygen into MBE-grown AlGaAs layers was systematically studied by changing the growth temperature and AlAs mole fraction. It was found that segregation of oxygen atoms strongly influences oxygen incorporation. By taking into account the surface segregation of oxygen, all of the particular characteristics observed in the oxygen incorporation into MBE-grown AlGaAs layers can be explained including a peak and a dip formation in the profile. Oxygen atoms accumulate on the surface of the substrate due to surface segregation and the number multiplied by the coefficient of surface segregation determines the oxygen incorporation. Introduction Reduction of residual oxygen in semiconductor layers, such as AlGaAs and InAlGaP, is very important for optical device fabrication because oxygen forms nonradiative recombination centers in these materials [1,2]. There are many reports about the deterioration of devices due to the incorporation of oxygen, but few have studied the incorporation mechanism itself. Achtnich et al. reported that oxygen segregates in AlGaAs layers and accumulates at the interfaces, which decreases the mobility of modulated-doped electrons at GaAs/AlGaAs inverted interfaces [3]. Excessive oxygen segregation also causes interface roughness and deteriorates AlAs/(Al)GaAs Bragg reflectors [4]. Kuech et al. studied oxygen incorporation during metalorganic vapor phase epitaxial growth of GaAs [5]. They used an Al-based precursor, (C2H5)2AlOC2H5, and found that when the oxygen incorporation exceeded 1018 cm-3, the periodic surface structure broke down and the surface had a very rough hillock structure. In spite of these phenomenological studies, there are few systematic studies about the incorporation of oxygen itself. To better understand the incorporation mechanism of oxygen, we systematically studied the incorporation mechanism by changing the growth parameters and AlAs mole fractions during molecular beam epitaxy (MBE) of AlGaAs layers, and determined the depth profile of oxygen using secondary ion mass spectrometry (SIMS). Experimental Multilayer structures of GaAs, AlGaAs, and AlAs layers were grown on n-type (001) GaAs substrates by MBE with a range of growth parameters. Prior to insertion into the MBE system, the substrates were prepared with a conventional treatment that consisted of degreasing,
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acid etching, rinse in deionized water, and a dry N2 blow. The substrate was soldered to a Mo block using high-purity In. This was done under N2 ambient to avoid introducing excess oxygen into the system. The surface oxide on the substrates was thermally desorbed in vacuum, and the desorption temperature was assumed to be 580 oC as a temperature cal
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