MBE Growth of III-V Nitride Thin Films and Quantum Well Structures

摘要

GaN has been grown by MBE at growth rates up to 1 #mu#m/hr and at temperatures up to 950 deg C using a new rf nitrogen plasma source developed by EPI, Inc. The GaN films show excellent optical properties and can be doped n-type with Si and p-type with Mg at high temperatures. Low temperature photoluminescence measurements yield an optical ionization energy for the Mg acceptor in GaN of about 224 meV. Special techniques have been developed for the growth of InGaN quantum wells. The growth of high quality InGaN is complicated by thermodynamic limitations: InN is unstable and tends to dissociate at typical MBE growth temperatures of 600-800 deg C. To overcome these difficulties, we have developed a modulated beam technique which employs alternating layers of (In,Ga)N and (Ga)N, analogous to the techniques used for the growth of InGaN by MOVPE. The intermittent deposition of a brief GaN layer stabilizes the indium containing layer before droplets can nucleate and results in high quality epitaxy. Uxing this technique, GaN/InGaN quantum well structures have been synthesized which emit narrow (FWHM approx 20-30 nm) photoluminescence and electroluminescence in the violet-to-green spectral regions at room temperature.