Luminescence of GaN single crystals prepared by heating a Ga melt in Na–N2 atmosphere

✍ Scribed by Takahiro Yamada; Hisanori Yamane; Takenari Goto; Takafumi Yao; Yongzhao Yao; Takashi Sekiguchi

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 159 KB
• Volume: 42
• Category: Article
• ISSN: 0232-1300
• DOI: 10.1002/crat.200610893

✦ Synopsis

Abstract

Colorless transparent prismatic crystals (0.5‐2.0 mm long) and hopper crystals (1.0‐2.5 mm long) of GaN were prepared by heating a Ga melt at 800°C in Na vapor under N~2~ pressures of 7.0 MPa for 300 h. The photoluminescence (PL) spectrum of a prismatic crystal at 4 K showed the emission peaks of neutral donor‐bound exciton (D^0^‐X) and free exciton (X~A~) at 3.472 eV and 3.478 eV, respectively, in the near band edge region. The full‐width at half‐maximum (FWHM) of (D^0^‐X) peak was 1.9 meV. The emission peaks of a donor–acceptor pair transition (D^0^‐A^0^) and its phonon replicas were observed in a lower energy range (2.9‐3.3 eV). The emission peaks of the D^0^‐A^0^ and phonon replicas were also observed in the cathodoluminescence (CL) spectrum at 20 K. The (D^0^‐X) PL peak of a hopper crystal at 4 K was at 3.474 eV (2.1 meV higher), having a FWHM of 6.1 meV which was over 3 times larger than that of the prismatic crystal. A strong broad band with a maximum intensity around 1.96 eV was observed for the hopper crystals in the CL spectrum at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)