Growth of high-temperature AlN and AlGaN layers on sapphire substrates using ammonia MBE

Yu. V. Grishchenko, I. S. Ezubchenko, M. L. Zanaveskin, I. O. Mayboroda, M.Y u. Presniakov

 National research centre "Kurchatov institute"

 

 The paper is received on December 30, 2015

 

Abstract. Epitaxial films and III-nitrides heterostructures (AlN, GaN) have found a wide application at micro and optoelectronics. The properties of AlN and AlGaN high-temperature (HT) films growths on sapphire substrates by means of ammonia MBE were studied at this paper.  Reflective high energy electron diffraction (RHEED), atomic-force microscopy (AFM), transmission electron microscopy (TEM) and X-Ray diffraction were used to study the properties of epitaxial films. It was found that density of hillocks in HT AlN layers on sapphire can be reduced from 3x10⁹ down to 2x10⁷ per cm² through the rise of the ammonia flux during growth process. It was shown that deposition of AlGaN films under high Ga desorption led to selective enhancement of lateral growth component at the areas of developed surface morphology. Enhanced lateral growth allowed to achieve accelerated transition to 2-D growth mode at the initial stages of growth and led to formation of stepped surface with terrace width of 1 micron. Also formation of threading pores was completely suppressed. On the basis of terrace-step-kink model (TSK model) the mechanism of lateral growth enhancement was suggested.

Key words: ammonia MBE, high electron mobility transistors, AlN, AlGaN, enhanced lateral growth.