Laser-Assisted Metal-Organic Chemical Vapor Deposition of Gallium Nitride

Ammonia (NH3) is commonly used as group-V precursor in gallium nitride (GaN) metal-organic chemical vapor deposition (MOCVD). The high background carbon (C) impurity in MOCVD GaN is related to the low decomposition efficiency of NH3, which represents one of the fundamental challenges hindering the development of high-purity thick GaN for vertical high-power device applications. This work uses a laser-assisted MOCVD (LA-MOCVD) growth technique to address the high-C issue in MOCVD GaN. A carbon dioxide (CO2) laser with a wavelength of 9.219 mu m is utilized to facilitate NH3 decomposition via resonant vibrational excitation. The LA-MOCVD GaN growth rate (GR; as high as 10 mu m h(-1)) shows a strong linear relationship with the trimethylgallium (TMGa) flow rate, indicating high effective V/III ratios and, hence, efficient NH3 decomposition. [C] in LA-MOCVD GaN films decreases monotonically, as the laser power increases. A low [C] at 5.5 x 10(15) cm(-3) is achieved in the LA-MOCVD GaN film grown with GR of 4 mu m h(-1). LA-MOCVD GaN films reveal high crystalline quality with room-temperature mobility of >1000 cm(2) V(-1 )s(-1). LA-MOCVD provides an enabling route to achieve high-quality GaN epitaxy with low-C and fast GR simultaneously. This technique can be extended for epitaxy of other nitride-based semiconductors.