Nanopatterning of GaAs(110) vicinal surfaces by hydrogen-assisted MBE
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Nanopatterning of GaAs(110) vicinal surfaces by hydrogen-assisted MBE M.L. Crespillo, J.L. Sacedón, B.A. Joyce1 and P. Tejedor Instituto de Ciencia de Materiales de Madrid, Cantoblanco , 28049 Madrid, Spain 1 Department of Physics, Imperial College London, Blackett Laboratory, London SW7 2AZ, United Kingdom
ABSTRACT The effect of atomic hydrogen on the growth mode and surface morphology of GaAs(110) thin films grown by molecular beam epitaxy (H-MBE) has been studied for different kinetic regimes using atomic force microscopy (AFM). Growth in the Ga supplylimited regime after H-assisted oxide removal leads to the formation of multi-atomic step arrays by step bunching with a very uniform terrace size distribution in the 80 nm range. Growth under As-deficient conditions after H-assisted oxide removal induces a rapid selforganization of the GaAs(110) surface into a ridge pattern along the tilt direction, which is broken down into a 3D mound morphology when H is also present during growth. A chacteristic nanofacetting of the surface with very straight -type steps is observed at high temperatures regardless of atomic hydrogen being used during oxide desorption and/or epitaxial growth.
INTRODUCTION Homoepitaxial growth of GaAs on (110) vicinal surfaces under different kinetic regimes leads to the formation of a wide variety of pattern-forming instabilities associated with step propagation in the presence of Ehrlich-Schwoebel (E-S) barriers at step edges [1,2]. In particular, the formation of step bunches typically observed at low growth rates and temperatures is kinetically controlled by the arrival rate of Ga atoms to the vicinal surface during epitaxy (Ga supply-limited regime) [3]. On the other hand, growth under Asdeficient conditions at higher temperatures is kinetically controlled by the incorporation rate of As-containing species to step edges, which occurs preferentially from the terrace below, creating a ripple pattern by the Bales-Zangwill mechanism [4]. As growth proceeds, a secondary instability sets in and ripples break up into 3D pyramidal mounds that eventually self-organize into a well-ordered pattern on the surface [5]. In recent years, utilization of atomic hydrogen during MBE growth has been shown to induce the formation of self-organized one-dimensional step arrays on high-index GaAs substrates [6,7]. In this paper we explore the utilization of atomic hydrogen during MBE growth as a possible means of obtaining laterally ordered nanopatterns on the GaAs (110) surface misoriented by 2º towards (111)A. Atomic Force Microscopy (AFM) has been used to study the changes undergone by this surface, in both growth mode and morphology, during GaAs homoepitaxy under different kinetic regimes when i) native oxide removal is carried out at low temperatures under a flux of atomic hydrogen, but growth is carried out by conventional MBE growth and ii) when both oxide removal and epitaxial growth are carried out in the presence of atomic hydrogen.
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EXPERIMENTAL DETAILS The experiments were carried ou
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