Optical properties of GaN grown by hydride vapor-phase epitaxy.

High-quality free-standing GaN was obtained by hydride vapor-phase epitaxy (HVPE) growth and the subsequent removal of the sapphire substrates. In the photoluminescence (PL) spectra of the as-grown HVPE-GaN, we observed a strong phonon replica peak for temperatures higher than 80 K. Both the near-band-edge emission and the yellow emission in the cathodoluminescence spectra were inhomogeneous, and correlated with the crystalline structure. With the homoepitaxial regrowth by metal-organic chemical-vapor deposition (MOCVD) in the GaN substrates, these unusual optical properties were no longer observed and the PL peak became sharper than GaN grown by MOCVD on sapphire substrates, indicating that the free-standing GaN is suitable as substrates for the growth of device structures. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]