High-resolution emission spectroscopy of random lasing in GaN films pumped by UV-pulsed laser

We report on room temperature photoluminescence on GaN films grown by metal organic chemical vapor deposition (MOCVD). A NdYAG pulsed-laser at 266 nm illuminates the films. Two components, at 363 nm and 370 nm, are identified in the near band edge structure on the spectra. A laser threshold of 700±150 kW cm−2 is evidenced and corresponds to random lasing in the GaN film. A drastic narrowing of the spectral bandwidth from 5.2 to 1.8 nm is observed at 370 nm. High-resolution spectroscopy measurements show laser mode widths thinner than 50 pm leading to a high quality factor Q=7750. Low-resolution measurements show redshift from 370.0 to 373.1 nm for one component and from 363.1 nm to 363.9 nm for the other. Interpretation of this redshift is discussed.