Pulsed laser deposition of GaN thin films

Gallium nitride thin films were grown via pulsed laser deposition (PLD) in different atmospheres (N2, NH3 and ultra-high-vacuum) on sapphire. Resistivity, doping and Hall mobility of the films are studied as a function of temperature and growth conditions: we found that the films grown in ammonia have n-type (n≈1016 cm−3) background doping, while growth in N2 (p≈1013 cm−3) and in UHV (p≈1019 cm−3) induces p-type doping. The surface quality of the films is also investigated by atomic force microscopy (AFM) and the values for surface roughness are of the order of tens of nanometers for the films grown in ammonia while films grown in N2 have a roughness of few nanometers.