Observation of resonant Raman lines during the photoluminescence of doped GaN

Abstract

P-type doping of molecular beam epitaxy grown GaN has been investigated using beryllium, magnesium and carbon, the sample being characterized by luminescence under optical excitation by He-Cd laser light of energy 3.815 eV. Doping resulted in a strong reduction of the band-edge luminescence 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 positions 3.541, 3.449, 3.357 and 3.266 eV in a wide variety of these samples. 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 separated by the GaN longitudinal optical phonon energy of 92 meV. It is believed that these lines are caused by resonant Raman scattered replicas appearing in the photoluminescence spectra.

Properties of GaN epitaxial layers grown on 6H-SiC(0001) by plasma-assisted molecular beam epitaxy

“…11 were all acquired using He-Cd excitation. An intense line at 3.448 eV is seen in the spectra, and from comparison with similar spectra acquired with frequency-doubled Ar laser excitation we can identify this feature as arising from the He-Cd laser line which is Raman shifted by multiple GaN longitudinaloptical phonon energies, in agreement with the identification of Dewsnip et al [25] .…”

First-principles studies of beryllium doping of GaN

“…This conclusion is in agreement with the assessment of Bernardini et al 6 Experiments on Be incorporation in GaN are still scarce. Incorporation of Be in GaN has so far been performed during MBE growth [7][8][9][10][11][12][13][14][15] and using ion implantation. 16,17 The earliest report of Be doping was by Ilegems and Dingle, 47 who incorporated Be during vapor growth of GaN.…”

“…[7][8][9][10][11][12][13][14][15] These experimental studies have involved both wurtzite and cubic phases of GaN; the cubic phase can be obtained by growth on cubic substrates, under appropriately tailored conditions. Another technique for Be incorporation that has been attempted is ion implantation.…”

Ammonothermal synthesis of GaN doped with transition metal ions (Mn, Fe, Cr)

“…The identification of the process taking part in this resonance is far beyond the scope of this paper and will be published elsewhere. This characteristic set of LO phonon replicas of excitation energy was also recorded in GaN crystals doped with Be, Mg, C acceptors excited by He-Cd laser (3.813 eV) [65].Thus, the observation of resonant Raman scattering cannot be related to specific properties of Mn acceptor, but rather to dramatic decrease of PL intensity in AMMONO GaMnN. Acceptors in general may be responsible for the observed effect.…”