SUPERSONIC-JET-ASSISTED GROWTH OF GAN AND GAAS FILMS

We present the results of investigations of the growth of two semicond uctor materials using supersonic jets. Homoepitaxial growth of GaAs fi lms was accomplished by directing a supersonic jet of the single sourc e precursor (t-Bu)(2)(Ga-As)(t-Bu)(2) seeded in helium at a heated GaA s(100) substrate. Epitaxial GaAs films were produced with substrate te mperatures of 400-500 degrees C,while a wafer temperature of 300 degre es C yielded degraded crystallinity in the deposited film. Atomic forc e microscopy revealed that the GaAs films were relatively smooth,, wit h a root mean square roughness of 8.1 Angstrom. We have also successfu lly grown GaN films on sapphire (0001) using supersonic jets of nitrog en atoms and a gallium effusion source. The nitrogen atoms were genera ted from a mixture of 1% N-2 in He by a radio frequency discharge. A g rowth rate of 0.65 mu m/h was obtained, independent of substrate tempe rature over the range 600-750 degrees C. The films were single crystal line wurtzite GaN as determined by x-ray diffraction and in situ refle ction high energy electron diffraction (RHEED). The peak width of the (0002) GaN re flection, as measured by high resolution x-ray diffracti on, was as low as 38 arcmin, indicating a crystalline quality that is comparable to GaN films deposited by other plasma-assisted molecular b eam epitaxy techniques, but inferior compared to films currently grown by metalorganic chemical vapor deposition. In addition, the peak widt h decreases with increasing growth temperature, indicating that the cr ystalline quality of the film improves. The RHEED images also indicate that the GaN films have a rough surface morphology. (C) 1996 American Vacuum Society.