Photoluminescence and Excitation Spectra of Deep Defects in GaN

Deep defects responsible for broad bands in the red-to-green range of the photoluminescence (PL) spectrum of undoped and Si-doped GaN grown by molecular beam epitaxy (MBE) and hydride vapor phase epitaxy (HVPE) were studied by employing PL and PL excitation (PLE) methods. In HVPE grown samples, a red luminescence (RL) and a green luminescence (GL) bands were observed, respectively, at about 1.9 and 2.4 eV. Similar in positions but different in properties red and green bands (RL2 and GL2, respectively) dominated in the samples grown in Ga-rich conditions by MBE with radio frequency plasma as a nitrogen source (RF-MBE). A yellow luminescence (YL) with a maximum at about 2.2 eV dominated in the samples with ammonia used as a nitrogen source (NH 3 -MBE). It has been established from the variation of temperature, excitation intensity and excitation wavelength that the abovementioned five bands are related to different deep-level defects.