Deep Centers and Persistent Photoconductivity Studies in Variously Grown GaN Films

Journal of Applied Physics

et al. 2002

Concentrations of deep hole traps were measured in a set of hydride vapor phase epitaxy grown samples with thicknesses varying from 2.6 to 68 m. Results were obtained from low temperature capacitance-voltage measurements before and after illumination and from deep level transient spectroscopy measurements with optical injection ͑ODLTS͒. The former revealed the presence of high densities ͑ϳ10 15 to 10 16 cm Ϫ3 ͒ of hole traps whose concentration decreased with sample thickness in a manner similar to that found for the dislocation density. Capacitance versus temperature measurements in the dark and after illumination suggested that these traps form a band of states rather than a single level in the GaN band gap. It is suggested that such states could be associated with dislocations. The main hole traps observed by ODLTS were deep hole traps, of energy near E v ϩ0.9 eV. Their density was also observed to substantially decrease with sample thickness.

“…This behavior is similar to that already described for a set of MOCVD and HVPE grown samples in Ref. 8. It is explained by the capture of holes by deep acceptor states near the surface.…”

Section: Resultssupporting

confidence: 88%

“…Similar observations were previously reported in Ref. 8 for HVPE and MOCVD grown n-GaN films with high dislocation densities.…”

Section: Fig 2 1/csupporting

confidence: 91%

Section: Fig 2 1/cmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Deep hole traps in n-GaN films grown by hydride vapor phase epitaxy

Journal of Applied Physics

et al. 2002

Deep electron and hole traps in freestanding n-GaN grown by hydride vapor phase epitaxy

Journal of Applied Physics

et al. 2002

Deep level electron and hole traps were studied by means of deep level transient spectroscopy with electrical and optical injection on a freestanding thick n-GaN sample with low dislocation density. It is shown that at both the upper and the lower surface of the sample there exists a thin, ϳ0.5 m layer of damaged material with lowered concentration of electrons and enhanced density of deep centers. Deep in the bulk of the film the densities of the majority of the electron and hole traps are shown to be very low, but measurably higher on the lower face ͑N face͒, which was originally closer to the Al 2 O 3 substrate. The two faces are also shown to similarly differ in the density of deep hole traps whose concentration is deduced from low-temperature capacitance-voltage measurements in the dark and after illumination ͑such traps were previously associated with dislocation states͒. The concentration of persistent photocapacitance centers is shown to be very low on both sides and considerably lower than previously reported for other n-GaN samples with higher dislocation densities. Electron beam induced current measurements on both sides of the sample reveal the presence of dark spots whose density roughly correlates with the density of dislocations at the upper and lower faces. The reverse current at high voltages is shown to be considerably higher on the N face. The possible relationship of the observed phenomena to dislocations is discussed.

GaN as a detector of α-particles and neutrons

Quantum Sensing and Nanophotonic Devices VIII

et al. 2011

Properties of GaN radiation detectors are analyzed. It is shown that present day epitaxial material is suitable for detection of α-particles with the charge collection efficiency close to 100%. Such detectors can operate at temperatures of at least 60 o C and withstand irradiation with reactor neutrons fluences higher than 10 15 cm -2 . They keep the collection efficiency at 30% even after irradiation with 2×10 16 cm -2 neutron fluence. Registration of thermal neutrons with GaN detectors can also be achieved by using 10 B converter and the efficiency of registration is determined by the 10 B conversion efficiency from neutrons to low energy a-particles.