Low-Temperature Growth and Structural Characterization of GaAs Using Ionized Source Beam Epitaxy
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ABSTRACT Single-crystal GaAs films were grown on SI (100) GaAs at substrate temperatures below 200 TC by using ionized source beam epitaxy. The correlation between the properties of the films and the growth parameters, in particular, the substrate temperature, the amount of As-source beam ionization, and the acceleration voltage of the As beam was investigated to elucidate the possible benefits of source beam ionization and acceleration on low-temperature thin film growth. The use of ionized and accelerated As-source beam greatly improved the quality of the lowtemperature grown GaAs film. The surface morphology, crystallinity, and microstructure of the low temperature grown GaAs films were evaluated using in situ reflection high energy electron diffraction, double crystal X-ray diffraction, and cross section transmission electron microscopy.
INTRODUCTION Low temperature (LT) GaAs has been used to eliminate sidegating effects in GaAs metal semiconductor field-effect transistor (MESFET) devices [1]. The GaAs layers grown at a substrate temperature of -200 TC by molecular beam epitaxy (MBE), and annealed at -600 'C, show a high resistivity, a large trap density, and a breakdown strength about ten times that of semi-insulating (SI) GaAs [2]. And it is advantageous to grow at low substrate temperature in order to reduce the dopant diffusion and the segregation of undesirable impurities, and improve the interface roughness. However, there has been a little report on the growth of good quality GaAs with the substrate temperature of below 200 TC [3]. As reported by Yun et al. [4], the epitaxial growth of GaAs on (100) Si was investigated using ionized source beam epitaxy (ISBE) at growth temperatures in the range 160-280 °C. Yun et al. [5] also reported that the ionization and acceleration of the As-source beam greatly enhances 2D growth of GaAs on (100) Si and suppresses the formation of antiphase domain. In this work, the epitaxial growth of LT-GaAs is investigated using ISBE [6] at growth temperatures in the range 150-200 TC. The objective is to elucidate the effect of ionization and acceleration of source beam on the growth of GaAs epitaxial layers at the low temperature. Since As is known to exhibit a low sticking probability during the GaAs growth, only the As-source beam was partially ionized and then accelerated in the present work. To facilitate beam focusing and ionization, the As beam was produced using a supersonic nozzle. The effect of ionization and acceleration of source beam was evaluated in comparison with the source beam, which is similar to the normal MBE growth method. EXPERIMENT Transmission electron microscopy (TEM), double-crystal X-ray diffraction (DCXRD), and 23 Mat. Res. Soc. Symp. Proc. Vol. 399 01996 Materials Research Society
the scanning electron microscopy (SEM) studies were performed on three kind of samples of LT-GaAs substrates grown at a temperature of 200 TC. All samples were unannealed. The films used in this study were grown by a home-made ISBE system. The basic arrangement of the p
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