OBSERVATION OF RESONANT RAMAN LINES DURING THE PHOTOLUMINESCENCE OF DOPED GAN

P-type doping of molecular beam epitaxy grown GaN has been investigate d using beryllium, magnesium and carbon, the sample being characterize d by luminescence under optical excitation by He-Cd laser light of ene rgy 3.815 eV. Doping resulted in a strong reduction of the band-edge l uminescence in some samples and the appearance of deep level bands at around 2.3 and 2.5 eV. Photoluminescence spectra in the region of the band gap using high gain revealed the presence of narrow lines at posi tions 3.541, 3.449, 3.357 and 3.266 eV in a wide variety of these samp les. These lines were constant in position with respect to temperature over the range of 5 K to 300 K and it was noted that they are separat ed by the GaN longitudinal optical phonon energy of 92 meV. It is beli eved that these lines are caused by resonant Raman scattered replicas appearing in the photoluminescence spectra.