Photoluminescence and optical quenching of photoconductivity studies on undoped GaN grown by molecular beam epitaxy

Deep levels in undoped GaN materials grown by modified molecular beam epita xy (MBE) are investigated by photoluminescence (PL) and optical quenching o f photoconductivity measurements. A broad band which extends from 2.1 to 3. 0 eV with a maximum at about 2.7 eV is observed, and four prominent quenchi ng bands were found located at 2.18, 2.40, 2.71, and 2.78 eV above the vale nce band, respectively. These levels are attributed to four holes trap leve ls existence in the material. The defects cannot be firmly identified at pr esent. (C) 2000 Elsevier Science B.V, All rights reserved.