Luminescence spectroscopy of GaN in the high-temperature regime from room temperature to 900 °C

We have measured the optical luminescence spectrum of GaN from the near infrared to the near ultraviolet at elevated temperatures. Despite intense blackbody radiation above 600 °C, luminescence is observable at 3 eV or greater at temperatures as high as 900 °C, i.e., including near-band-edge emissions over the entire range of GaN growth temperatures. Elevated-temperature measurements also reveal thermally activated quenching of the midgap “yellow” defect luminescence. These results show that electron beams already used to monitor molecular-beam epitaxy growth can also provide temperature and defect information during the growth process.