Structural and electrical characteristics of epitaxial GaN thin films grown using pulsed laser deposition assisted by an atomic nitrogen source

A deposition system combining pulsed laser deposition (PLD, cooled Ga target) and a source of atomic nitrogen was developed to grow epitaxial gallium nitride on sapphire. The layers obtained with this system were characterized using high-resolution X-ray diffraction, atomic force microscopy (AFM), Hall effect, and secondary ion mass spectroscopy (SIMS). It is found that the crystal quality greatly depends on the atomic nitrogen flux incident on the substrate during growth. After optimization of the atomic nitrogen-to-gallium flux ratio, samples showing very narrow GaN(0 0 0 2) rocking curves (full width at half maximum, FWHM=80 arcsec) have been synthesized at a low substrate temperature (Ts=750°C). Surface analysis of these thin films, using AFM, also show a very low roughness (Rrms=14 Å).