GROWTH OF GABN TERNARY SOLUTIONS BY ORGANOMETALLIC VAPOR-PHASE EPITAXY

Layers of Ga1-xBxN with compositions from x = 0 to x = 0.07 were grown by organometallic vapor phase epitaxy on sapphire substrates using tr imethylgallium, triethylboron (TEE) and NH, as precursors. Growth was done in the temperature range from 450 to 1000 degrees C. The presence of boron was detected by the shift in the (0002) peak position in x-r ay diffraction, by x-ray photoelectron spectroscopy, secondary ion mas s spectrometry measurements, and by the changes in the band gap as mea sured by optical transmission. It was found that for the studied range of compositions the band gap varied from 3.4 eV for x = 0 to 3.63 eV for x = 0.05. At certain TEE concentrations in the gas phase, the grow th rate decreased abruptly, most likely because of a growth poisoning by the onset of growth of a very slow growing B-rich phase. The thresh old TEE concentration for this growth poisoning decreased with increas ing growth temperature; and at 1000 degrees C, less than 1% of B could be incorporated as a result. GaBN alloys with about 7% substitutional boron were also produced by implantation of 5 x 10(16) cm(-2) B ions at 60 keV into GaN, as evidenced by the shift of the band edge emissio n in cathodoluminescence spectra from 3.4 eV for GaN td 3.85 eV for Ga BN.