A Study on the Growth of Cubic GaN Films Using an AlGaAs Buffer Layer Grown on GaAs (100) by Plasma-Assisted Molecular B
- PDF / 629,589 Bytes
- 5 Pages / 595 x 842 pts (A4) Page_size
- 34 Downloads / 190 Views
A Study on the Growth of Cubic GaN Films Using an AlGaAs Buffer Layer Grown on GaAs (100) by Plasma-Assisted Molecular Beam Epitaxy Ryuhei KIMURA, Kiyoshi TAKAHASHI, and H. T. Grahn1 Department of Media Science, Teikyo University of Science and Technology 2525 Yatsuzawa, Uenohara, Kitatsuru-gun, Yamanashi, 409-0193, Japan 1
Paul Drude Institute for Solid State Electronics, Hausgvogteiplatz 5-7, 10117
Berlin, Germany
ABSTRACT An investigation of the growth mechanism for RF-plasma assisted molecular beam epitaxy of cubic GaN films using a nitrided AlGaAs buffer layer was carried out by in-situ reflection high energy electron diffraction (RHEED) and high resolution X-ray diffraction (HRXRD). It was found that hexagonal GaN nuclei grow on (1, 1, 1) facets during nitridation of the AlGaAs buffer layer, but a highly pure, cubic-phase GaN epilayer was grown on the nitrided AlGaAs buffer layer.
INTRODUCTION Metastable cubic-GaN (β-GaN) is expected to have many advantages in its physical properties over those of the hexagonal phase including lower resistivity and higher doping efficiency due to its higher crystallographic symmetry. For the growth of β-phase material, MBE has been found to be the most suitable growth method due to its non-thermal equilibrium nature. As such, many researchers have been investigating cubic-GaN using MBE. Recently, the successful growth of high-quality, hexagonal GaN on sapphire by RF-MBE, which is comparable to that grown by MOCVD, was reported using an AlN buffer layer and AlN multi-intermediate layer [1,2]. These results suggest that an AlN or AlGaN buffer layer is effective to optimize the crystal quality of the MBE grown epilayer, although at present the role of Al is not clear. In this work, an AlGaAs buffer layer has been used to form an AlGaN surface by nitridation, and a highly pure, cubic-phase GaN film was successfully grown on the nitrided AlGaAs buffer layer.
G3.46.1
EXPERIMENTAL DETAILS Cubic GaN films were grown on semi-insulating GaAs (1, 0, 0) substrates by RF-MBE. Details of the pre-treatment procedure of the GaAs substrate have been described elsewhere [4]. After thermal annealing under As over-pressure conditions (1.0 x 10-5 Torr), the AlGaAs buffer layer was grown at 750 OC for 1 hour. The Ga, Al, and As cell temperatures were 830 850 OC, 1070 OC, and 365 OC, respectively. In this work, a new piece of equipment, namely a crystal cell (Eiko MB-3100C), which generates a very stable beam flux at the cell temperature lower than 500 OC, was employed as the As source. By using this cell, the crystallinity of the AlGaAs buffer layer was dramatically improved. The final layer thickness was around 1 µm. The Αl mole fraction was about 0.18 - 0.22 as determined by photoluminescence (PL) at 18 K. The nitridation was carried out using N-plasma exposure at a substrate temperature of 750 OC for 10 min. The N-plasma was supplied by RF-plasma source (Oxford CPD-21) operating at 300 W, and the N flow rate was 3 sccm. Subsequent to nitridation, the substrate temperature and RF power wer
Data Loading...
