Epitaxial growth of cubic GaN and AlN on Si(001)
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Internet Journal o f
Nitride S emiconductor Research
Volume 1, Article 21
Epitaxial growth of cubic GaN and AlN on Si(001) A. Barski, U. Rössner, J. L. Rouviere, M. Arlery CEA/Grenoble, Département de Recherche Fondamentale sur la Matière Condensée/SP2M This article was received on June 3, 1996 and accepted on October 24, 1996.
Abstract Thermal treatment under propane at 1300-1400 °C has been used to prepare Silicon (001) wafers for subsequent growth of cubic GaN and AlN by Electron Cyclotron Resonance Plasma Assisted Molecular Beam Epitaxy (ECRMBE). Thermal treatment of Silicon wafers under propane, used in this experiment, produced a very thin (40 Å) layer of cubic SiC on the Silicon (001) surface. Despite an extremely low thickness of as-produced SiC layer, high quality cubic GaN has been successfully grown. The cubic form of AlN grown on the SiC(40Å)/Si(001) surface has also been observed despite a very high density of stacking faults.
1. Introduction Silicon is one of the most attractive substrates for the future implementation of GaN and/or AlN -based devices, allowing integration of silicon based circuits on the same substrate. However, during the growth of GaN, one has to face serious problems: GaN can occur in either the hexagonal (wurtzite) or the cubic (zincblende) structures, and both polytypes often appear in the same epitaxial layer, leading to stacking faults. Moreover, GaN has a large lattice mismatch to substrates currently used in microelectronics like Si and GaAs (16.6% and 19.9% respectively). GaN films have been grown epitaxially on Si(001) by Electron Cyclotron Resonance Microwave Plasma-Assisted Molecular Beam Epitaxy (ECR-MBE) using a thick SiC buffer layer [1] [2]. Direct growth of GaN on a clean Si(001) 2x1 surface results in highly polycrystalline material; the case for which true epitaxy has been observed is for the growth on Si(001) surface covered by small crystallites of SiC formed during the Si(001) substrate annealing [3], and on the unreconstructed (i.e., 1x1 ) Si(001) surface [4] [5] . However, in the reflection high-energy electron diffraction (RHEED) image of an unreconstructed Si(001) surface [4] [5] one can clearly observe the spots characteristic of the presence of cubic SiC crystallites. Cubic GaN grown on the Si(001) surface covered by SiC crystallites has some misoriented domains [4] and the full width at half-maximum (FWHM) of the x-ray rocking curve of the (002) peaks of 4 and 1 µm thick films of GaN are as wide as 60 and 90 min. respectively [4]. In the present paper we report growth of cubic GaN and AlN on the Silicon (001) surface covered by a very thin (40 Å) epilayer of SiC. This thin epilayer of SiC is produced on the Silicon (001) surface by thermal treatment of Si(001) substrates under propane at 1300-1400 °C. The results described below clearly show that high quality cubic GaN can be successfully grown using this relatively simple procedure for the Silicon (001) surface preparation. The quality of as grown GaN is comparable to the quality of GaN grown on a
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