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1 Opto-Electronics Review

1 2004

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Carrier transport in GaN single crystals and radiation detectors investigated by thermally stimulated spectroscopy

Kažukauskas V., Vaitkus J. V.

Opto-Electronics Review

2004

Vol. 12, No. 4

399-403

We investigated single crystals of GaN and thin film GaN radiation detectors by thermally stimulated currents (TSCs) and thermally stimulated depolarization (TSD) methods in order to characterize carrier transport properties as influenced by material defect structure. In thick GaN, no expressed structure of the TSC spectra was observed in the temperature range from 100 K up to 350 K that could be characteristic for thermal carrier generation from trap levels. The experimental facts imply that TSC spectra might be caused not by carrier generation from traps, but it could be due to thermal mobility changes. Therefore we had applied the numerical analysis by taking into account carrier scattering by ionized impurities and by phonons. It was found that mobility limited by ionized impurities varies as ~ T2.8 and lattice scattering causes the dependence ~ T -3.5. The highest mobility values were up to 1550 cm² /Vs at 148-153 K. Such high values indicate relatively good quality of the single GaN thick crystals. In high resistivity GaN detectors irradiated by high doses of high-energy neutrons and X-rays current, the instabilities were observed that could be caused by the change of carrier drift paths in a highly disordered mater. A model of carrier percolation transport is presented.