The influence of deposition parameters on the structural quality of PLD-grown GaN/sapphire thin films

Abstract

Epitaxial GaN thin films are grown on conventional sapphire (0001) substrates using pulsed laser deposition in five different sets. The evolution of crystallization and surface morphology of the as-deposited films is studied to evaluate the influence of growth conditions such as: substrate heating, background N2 pressure, target-substrate distance, laser energy density, and substrate location, which were systematically varied. Upon the optimization of process conditions, E2-h Raman peak red-shifts toward the unstrained 567.6cm−1 location are observed, accompanied with an increase in texture coefficient of (0002) orientation, a decrease in average surface roughness to values less than 3nm, and threading dislocations density in the order of ∼3×109cm−2. This study accounts for the physics behind the careful tuning of PLD parameters as an approach to optimize the structural quality of GaN grown films on conventional sapphire substrates. The results could be a reference for further growth complications in PLD.