MIJ-NSR Vol. 9, Art. 2, V. Noveski et al.

Growth of AlN crystals on AlN/SiC seeds by AlN powder sublimation in nitrogen atmosphere

V. Noveski
Department of Materials Science and Engineering, North Carolina State University
and
Department of Chemical and Materials Engineering, Arizona State University

R. Schlesser
Department of Materials Science and Engineering, North Carolina State University

S. Mahajan
Department of Chemical and Materials Engineering, Arizona State University

S. Beaudoin
School of Chemical Engineering, Purdue University

Z. Sitar
Department of Materials Science and Engineering, North Carolina State University

This article was received on and accepted on Monday, February 9, 2004.

Abstract

AlN single crystals were grown on AlN/SiC seeds by sublimation of AlN powder in TaC crucibles in a nitrogen atmosphere. The seeds were produced by metallorganic chemical vapor deposition (MOCVD) of AlN on SiC crystals. The influence of growth temperature, growth time and source-to-seed distance on the crystallinity and the crystal growth rate were investigated. Crystals were grown in an RF heated sublimation reactor at growth temperatures ranging from 1800-2000°C, at a pressure of 600 Torr, nitrogen flow-rate of 100 sccm and source-to-seed distances of 10 and 35 mm. At 1870°C and a source-to-seed distance of 35 mm, isolated crystals were observed with few instances of coalescence. At 1930°C, a source-to-seed distance of 10 mm and longer growth times (~30 hrs), crystal coalescence was achieved. Above 1930°C, the decomposition of SiC was evidently affecting the growth morphology and resulted in growth of polycrystalline AlN. After an initial nucleation period, the observed growth rates (10-30 µm/hr) were in close agreement with predictions of a growth model that assumed gas-phase diffusion controlled growth. Optical and electron microscope observations revealed step-flow growth, while X-ray diffraction results showed the single crystal nature of the grown material. Single crystalline AlN was grown over surface areas of 200-300 mm² and was transparent and essentially colorless.

Outline

Introduction

Experimental set-up and procedure

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Cite this article as: MRS Internet J. Nitride Semicond. Res. 9, 2(2004).

last updated Monday, March 1, 2004 4:13:48 PM.