| Title |
Carrier dynamics in neutron-irradiated gan epitaxial layers |
| Translation of Title |
Krūvininkų dinamika neutronais apšvitintuose GaN epitaksiniuose sluoksniuose. |
| Authors |
Petrusevičius, Gustas |
| Full Text |
|
| Pages |
50 |
| Keywords [eng] |
Irradiation, GaN, gallium nitride, LITG, TIPL, PL, carrier dynamics, point defects, defects, photoluminescence, laser-induced transient grating, spectroscopy, galio nitridas, spektroskopija, taškiniai defektai, defektai, fotoliuminescencija |
| Abstract [eng] |
In this work, the influence of neutron irradiation on carrier dynamics and recombination processes in gallium nitride (GaN) epitaxial layers grown on ammonothermal GaN substrates is investigated. A series of samples irradiated with different neutron doses ranging from 10¹² to 10¹⁷ neq/cm² was analyzed. Carrier transport was evaluated using laser-induced transient grating (LITG) spectroscopy, which allows the ambipolar diffusion coefficient and carrier lifetime to be determined. Recombination processes and changes in quantum efficiency were studied using time-integrated photoluminescence spectroscopy measurements performed in an integrating sphere. The obtained results showed that neutron irradiation does not have a significant effect on the ambipolar diffusion coefficient, but strongly reduces the carrier lifetime, especially from 10^¹⁵ neq/cm² upwards. This indicates that irradiation-induced point defects act as effective non-radiative recombination centers, while not significantly changing carrier mobility in the material. In heavily irradiated samples, a LITG hysteresis effect was also observed. It was associated with local defect heating and recombination-enhanced defect reaction effects. Meanwhile, photoluminescence measurements showed strong quenching of both band-to-band and defect-related emission bands, as well as a decrease in quantum efficiency with increasing irradiation dose. This is attributed to point defects and defect complexes formed during irradiation, which introduce additional energy levels in the band gap, enhance non-radiative recombination, and increase the probability of self-absorption of emitted photons. |
| Dissertation Institution |
Vilniaus universitetas. |
| Type |
Master thesis |
| Language |
English |
| Publication date |
2026 |
