Micro-Raman and photoluminescence studies of neutron-irradiated gallium nitride epilayers

Abstract

GaN epilayers grown on sapphire substrate were irradiated with various dosages of neutrons and were characterized using Micro-Raman and photoluminescence. It was found that the A 1 ͑LO͒ peak in the Raman spectra clearly shifted with neutron irradiation dosage. Careful curve fitting of the Raman data was carried out to obtain the carrier concentration which was found to vary with the neutron irradiation dosage. The variation of the full width at half maximum height of the photoluminescence was consistent with the Raman results. The neutron irradiation-induced structural defects ͑likely to be Ge Ga ͒ give rise to carrier trap centers which are responsible for the observed reduction in carrier concentration of the irradiated GaN.

Defect studies on fast and thermal neutron irradiated GaN

“…Both samples show an additional broad band around 3 eV which is not present in the virgin sample. Although other authors [12,13] have assigned a blue band around 2.9 eV to Ge Ga related transitions, we believe that this broad band is related to defects caused by the irradiation/annealing treatment since we also see a band in this region for sample 480f where transmutation doping was suppressed. Furthermore, such a blue band is frequently seen in as-grown and ion implanted samples [14].…”

Review of using gallium nitride for ionizing radiation detection

“…114 Neutron irradiation can also alter the resistivity or even cause type-reversion of the material. Compensation schemes have been identified for both p-type 115 and n-type 116 GaN when the neutron fluence exceeds 10 16 cm…”

“…Wang et al 116 suggested that the neutron-irradiation-induced structure defects Ge Ga give rise to carrier trap centers that are responsible for the observed reduction in the carrier concentration in irradiated n-type GaN. Due to these induced defects, trapping centers are created, and the Fermi level is pinned within the energy levels of these defects.…”

(Invited) Neutron Irradiation Effect on GaN-Based Materials

“…This result shows that the deep levels related to the BL band are unstable, and it has been changed by neutron irradiation. The origin of the BL band in as-irradiated GaN is attributed to the neutron transmuted Ge atom at Ga sites (29) , which is different from that of as-grown sample. After annealed, the formation of some new deep center leads to the dominance of nonradiative recombination.…”