GaN growth by a hot filament metalorganic vapor phase deposition technique

Abstract

GaN layers were grown on c-plane sapphire by metalorganic vapor phase epitaxy (MOVPE) using a hot tungsten filament for the ammonia (NH3) precracking. A two flows horizontal growth chamber was specially designed to eliminate parasitic reactions between TMG and NH3 and avoid TMG decomposition on the hot tungsten array located between the upper ammonia inlet and the substrate. Samples were grown under different (N2:H2) carrier gas compositions for different filament temperatures ranging from 500 to 2500 K. The hot tungsten filament improves the efficiency of the NH3 decomposition. The ratio of the growth rates obtained with and without the filament is about 2. This improvement is related to the increase of NH2 radicals issuing from the decomposition of ammonia on the hot filament as predicted by thermodynamic calculations.