Annealing properties of vacancy-type defects in ion-implanted GaN studied by monoenergetic positron beams

Abstract

Defects in ion-implanted GaN and their annealing properties were studied by using monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and the positron lifetimes were measured for Si+, O+, and Be+-implanted GaN grown by the metal-organic chemical vapor deposition technique. First-principles calculations were also used to identify defect species introduced by the implantation. For as-implanted samples, the major defect species was identified as Ga vacancies and/or divacancies. An agglomeration of defects starts after annealing at 400 °C, and the defect profile shifted toward the surface with the open volumes of the defects increasing. The annealing properties of defects were found to depend on the ion species, and they are discussed here in terms of defect concentrations and interactions between impurities and defects.

Point defects in group-III nitride semiconductors studied by positron annihilation

“…2 shows the relationship between the S and W values for Be + -implanted GaN and highquality GaN grown by hydride vapor phase epitaxy (HVPE). The positron lifetime obtained for this sample was 15371 ps [15]. Since this lifetime is close to the lifetime of positrons that annihilate from the delocalized state, the spectrum for HVPE GaN was close to the characteristic one for defect-free GaN.…”

“…Ion-implanted samples were 4-mm-thick GaN films grown on (0 0 0 1) sapphire substrates by metalorganic chemical vapor deposition [15]. 18 keV Be + , 65 keV Si + , and 38 keV O + were implanted into the samples with a dose of 8.5 Â 10 14 cm À2 .…”

Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

“…The (S,W) values were calculated using the QMAS code for positron annihilation in defect-free (DF), Ga , and (Mg Ga ) 2 . The (S,W) values for Be-implanted GaN (GaN:Be) 20 and bulk GaN grown by an ammonothermal method (SCAAT) 41 are also shown. , the N A -N D value for the sample grown with the surfactant was higher than that for the sample without the surfactant.…”

“…Positron annihilation, a powerful technique for evaluating vacancy-type defects in semiconductors, 17,18 has been used to investigate defects in group-III nitrides. [19][20][21][22][23][24][25][26] In the present study, we used a monoenergetic positron beam to probe native vacancies in Mg-doped GaN grown by NH 3 -based MBE.…”

“…The total count of the coincidence Doppler broadening spectrum was 3 Â 10 6 . The relationship between S and E was analyzed using VEPFIT, a computer program developed by van Veen et al 30 (its application to GaN is described elsewhere 20,31 ). The S-E curve was fitted using…”