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 targe t) and a source of atomic nitrogen was developed to grow epitaxial gallium nitride on sapphire. The layers obtained with this system were characterize d using high-resolution X-ray diffraction, atomic force microscopy (AFM), H all effect, and secondary ion mass spectroscopy (SIMS). It is found that th e crystal quality greatly depends on the atomic nitrogen flux incident on t he substrate during growth. After optimization of the atomic nitrogen-to-ga llium 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 lo w substrate temperature (T-s = 750 degreesC). Surface analysis of these thi n films, using AFM, also show a very low roughness (R-rms = 14 Angstrom). ( C) 2001 Published by Elsevier Science B.V.