ECR-MBE and GSMBE of Gallium nitride on Si(111)
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U. ROSSNER, J.-L. ROUVIERE, A. BOURRET, A.BARSKI, D6partement de Recherche Fondamentale sur ]a Mati~re Condens6e/SP2M, CEA/Grenoble - 17, Rue des Martyrs - 38054 Grenoble Cedex 9, France. ABSTRACT Electron Cyclotron Resonance Plasma Assisted Molecular Beam Epitaxy (ECR-MBE) and Gas Source Molecular Beam Epitaxy (GSMBE) have been used to grow hexagonal GaN on Si (111). In the ECR-MBE configuration high purity nitrogen has been used as nitrogen source. In GSMBE ammonia was supplied directly to the substrate to be thermally cracked in the presence of gallium. By a combined application of in-situ reflection high-energy electron-diffraction (RHEED) and cross-sectional transmission electron microscopy (TEM) the growth mode and structure of GaN were determined. The growth mode strongly depends on growth conditions. Quasi two dimensional growth was observed in ECR-MBE configuration for a substrate temperature of 640'C while three dimensional growth occured in GSMBE configuration in the temperature range from 640 to 800'C. Low temperature (9 K) photoluminescence spectra show that for samples grown by ECRMBE and GSMBE a strong near band gap emission peak dominates while transitions due to deep level states are hardly detectable. The best optical results (the highest near band gap emission peak intensity) have been observed for samples grown by GSMBE at high temperature (800 0C). This could be explained by the increase of grain dimensions (up to 0,3 - 0,5 [tm) observed in samples grown by GSMBE at 800'C. INTRODUCTION The group III nitrides are intensively investigated because of their particular physical properties. Among them much interest is devoted to gallium nitride : its band-gap (Eg = 3.4 eV) gives access to optoelectronics in the blue and ultraviolet range [1] and its high thermal stability makes it an advantageous material for devices working at high temperature [2]. However, during the growth of GaN we have to face serious problems : GaN can occur in either hexagonal (wurtzite) or cubic (zinc blende) structure, and often both polytypes appear in the same epitaxial layer, leading to stacking faults. Moreover, it has a large lattice mismatch with substrates currently used in microelectronics like Si and GaAs (16.6% and 19.9% respectively). Relatively little work has been done on other substrates that AI2O,. Concerning silicon, Lei et al. [3] reported GaN growth on low temperature (400'C) GaN buffer layer, Watanabe et al. [4], Stevens et al. [5] and Meng et al. [6] reported GaN growth on AIN buffer layer on Si (111) by Electron Cyclotron Resonance Plasma assisted Molecular Beam Epitaxy (ECR-MBE) and Metal Organic Chemical Vapor Deposition (MOCVD). In the present paper we report GaN growth on AIN buffer layer on Si (111) by ECR-MBE and Gas Source Molecular Beam Epitaxy (GSMBE). The aim of this work is to compare structural and optical properties of GaN grown by ECR-MBE with GaN grown by GSMBE on Si (11) substrates.
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Mat. Res. Soc. Symp. Proc. Vol. 395 01996 Materials Research Society
EXPERIMENT The GaN and AIN fil
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