Effects of laterally overgrown n-GaN thickness on defect and deep level concentrations

Abstract

Electron capture behaviors of deep level traps in unintentionally doped and intentionally doped n-type GaNThe effects of the layer thickness and of Si doping on the dislocation type and density, electron concentration, and deep trap spectra were studied for epitaxially laterally overgrown ͑ELOG͒ GaN films with the ELOG region thickness varying from 6 to 12 m. Electron beam induced current imaging shows that for the thickest layers, the major part of the threading dislocations are filtered out while for thinner films they bend, but do not go out of play. The concentration of residual donors and major electron traps is found to decrease with increasing the film thickness. Si doping suppresses the concentration of the main electron trap with activation energy of 0.6 eV and enhances the concentration of the main hole trap at E v + 0.85 eV.

Electrical properties and deep traps spectra in undoped M-plane GaN films prepared by standard MOCVD and by selective lateral overgrowth

“…This strong decrease in traps concentration correlates very closely with a similar two orders of magnitude decrease of the dislocation density in the ELO and SELO films compared to m-GaN templates and points to a possible relation of such traps to dislocations. Similar observations have been reported for these traps in (0 0 0 1) GaN films grown by standard MOCVD and ELOG [9]. One can also note that decreasing the concentration of the E c À0.6 eV traps in laterally overgrown samples strongly increases the layers conductivity suggesting that these traps are major compensation agents.…”

“…Ref. [9]). The reason most likely is due to both a higher density of electron traps and lower density of hole traps in m-GaN layers.…”

Radiation Damage in GaN‐Based Materials and Devices

“…Deep level transient spectroscopy (DLTS) measurements performed on 1 MeV electron irradiated n-GaN showed the presence of deep electron traps with an activation energy of 0.9 eV attributed to N i acceptors [9]. The DLTS spectra of n-GaN irradiated with 60 Co γ-rays also showed the presence of electron traps G1 with activation energy 80 meV [10] close to that observed for V N donors in ref. [2].…”

“…The dependence of electron removal rate was also observed for variously doped n-GaN fi lms irradiated with 100 keV protons [47] and 60 Co γ-rays [48].…”

“…Comparison of electrical characteristics, deep traps spectra, diffusion length and MCL intensity of the low dislocation density (~5×10 6 cm -2 ) ELOG wing regions and high dislocation density (~10 8 cm -2 ) ELOG window regions was carried out by combined DLTS, ODLTS, MCL, EBIC measurements [51,[58][59][60]. For undoped n-GaN ELOG fi lms with the ELOG layer thickness of 12 μm, the residual donor concentration was much higher in the ELOG window region than in the ELOG wing region (~10 15 cm -3 versus ~3×10 14 cm -3 ), that the deep traps density in the ELOG wing region was about an order of magnitude lower than for standard MOCVD material, that the diffusion length in the low-dislocation-density ELOG wing was close to 0.3 μm versus 0.17 μm in the high-dislocation-density window (the lifetime difference of 0.4 ns versus 0.1 ns) and that the band-edge intensity was about 5 times higher in the ELOG windows [58].…”