Blue luminescence from amorphous GaN films deposited by pulsed-laser ablation at room temperature

Amorphous GaN (a-GaN) films were fabricated at room temperature using pulsed-laser ablation. The surface structure and chemical composition of the deposited films were strongly dependent on the Ar gas pressures and pulsed laser energies. The films deposited at the pressure of 10 Pa with 34 mJ/pulse were composed of an amorphous phase with a smooth surface. Under the same pressure, an increase in laser energy to 200 mJ/pulse resulted in a near stoichiometric GaN composition and an increase in crystallinity, without any significant change in surface structure. The room-temperature photoluminescence spectra confirmed that the a-GaN films exhibit blue-light emission at ∼2.8 eV, indicating that the highest luminescence efficiency was achieved from the nearly stoichiometric film deposited at 200 mJ/pulse under 10 Pa.