Effect of surface V2O5 nanolayers on the thermal oxidation kinetics of GaAs and the composition and morphology of resulting films

Abstract

INTRODUCTIONTransition metal oxide nanolayers on the surface of gallium arsenide are effective chemical stimulators of the oxidation of this semiconductor [1]. Depending on the deposition method (mild or harsh), V 2 O 5 on InP leads to different mechanisms of the thermal oxi dation of the semiconductor and, eventually, to differ ent properties of the resulting nanofilms [2,3]. Vana dium pentoxide deposited on the surface of GaAs by magnetron sputtering ensures oxidation by a catalytic mechanism [4]. The use of V 2 O 5 gel enables mild sur face modification of the semiconductor at relatively low temperatures and low energies. Before the thermal oxidation of a heterostructure, interaction between a chemical stimulator layer and components of the sub strate is negligible.The objectives of this work are to assess the kinetics and mechanism of the thermal oxidation of V x O y /GaAs heterostructures produced under mild conditions and determine the composition and sur face morphology of the resulting oxide films. EXPERIMENTAL Vanadium(V) oxide gel synthesized as described by Sladkopevtsev et al. [2] was dispersed using a compres sor disperser, which ensured the preparation of aerosol with a solution droplet size of up to 4-5 μm. The aero sol was deposited on Peltier cooled (111) AGChO n type GaAs semiconductor wafers with a 300 K majority carrier concentration of 5 × 10 16 cm -3 , which were pretreated with a 5 : 1 : 1 mixture of H 2 SO 4 (reagent grade, RF State Standard GOST 4204 77, 92.80%), Н 2 О 2 (extrapure grade, Purity Standard TU 6 02 570 750, 56%), and Н 2 О for 10 min and then rinsed repeatedly in double distilled water. The depo sition time was 3 min. The samples were dried in air. To crystallize amorphous films and remove water, the samples were annealed in air at 300°С for 120 min in an MTP 2M 50 500 resistively heated furnace. The temperature was controlled with an accuracy of ±1°С (OVEN TRM 10).The V x O y /GaAs heterostructures thus produced were oxidized in oxygen (30 L/h) at temperatures of 500, 530, 550, and 570°C for 60 min. The increase in the thickness of the films was determined every 10 min by laser ellipsometry (LEF 754, λ = 632.8 nm, abso lute uncertainty of ±1 nm). The thickness of the vana dium oxide layers was determined in the same way. To verify the laser ellipsometry data [5], the ellipsometric parameters of the films were measured as functions of wavelength on an Ellips 1891 spectral ellipsometer, and the inverse problem was solved using the Cauchy dispersion model [6]. The surface morphology of the Abstract-Vanadium(V) oxide, V 2 O 5 , produces a well defined chemical stimulation effect and can exhibit both oxygen transfer and catalytic behavior in the thermal oxidation of III-V semiconductors. Applying V 2 O 5 gel to the surface of GaAs is a mild surface modification method in which there is no interaction between the chemical stimulator layer and semiconductor substrate before thermal oxidation. Here, we describe the kinetics and mechanism of the thermal oxidation of V x O y /GaAs h...