HIGH GROWTH-RATE GAN FILMS USING A MODIFIED ELECTRON-CYCLOTRON-RESONANCE PLASMA SOURCE

GaN thin films were deposited by reactive molecular beam epitaxy metho d with a modified ASTeX(R) compact electron cyclotron resonance (ECR) plasma source of nitrogen. The effect of different ECR exit apertures on the growth rate and photoluminescence properties of GaN films was i nvestigated. An aperture with a matrix of 1.6 mm holes allowed for GaN films with good optical properties at growth rates up to 1 mu m/h. Ap ertures of larger diameter resulted in semi-insulating films. Room tem perature photoluminescence for both undoped and Si-doped GaN films wit h full width at half maximum less than 100 meV has been obtained at th e highest growth rates. We suggest that such an aperture effectively b locks the energetic ions from reaching the substrate thus reducing ion damage, resputtering, and increasing the Ga surface population. It al so creates a higher pressure inside the ECR resonator, and therefore, provides a higher flux of active species. While further optimization w ill result in better GaN film quality, our results suggest that the gr owth rate in Ga-rich condition is limited by the microwave power avail able in the ASTeX compact ECR source. (C) 1998 American Vacuum Society . [S0734-2101 (98)06105-3].