Annealing Behavior of Vacancy‐Type Defects in Mg‐ and H‐Implanted GaN Studied Using Monoenergetic Positron Beams

Abstract

Vacancy-type defects in Mg-implanted GaN with and without hydrogen (H) implantation are probed by using monoenergetic positron beams. Mg þ and H þ ions are implanted into GaN(000 1) to obtain 0.1 and 0.7-mm-deep box profiles with Mg and H concentrations of 1 Â 10 19 and 2 Â 10 20 cm À3 , respectively. For the as-implanted samples, the major defect species is determined to be Gavacancy (V Ga ) related defects such as V Ga , divacancy (V Ga V N ), and their complexes with impurities. For Mg-implanted samples, an agglomeration of vacancies starts at 800 C annealing, leading to the formation of vacancy clusters such as (V Ga V N ) 3 . For the samples annealed above 1000 C, the trapping rate of positrons by vacancies is increased by illumination of a He-Cd laser. This is attributed to the capture of photon-excited electrons by the defects and their charge transition. For Mg-and H-implanted samples, the hydrogenation of vacancy-type defects starts after 800 C annealing. Comparing with the annealing behavior of defects for the samples without H-implantation, the clustering of vacancy-type defects is suppressed, which can be attributed to the interaction between Mg, H, and vacancies.

Dopant activation process in Mg-implanted GaN studied by monoenergetic positron beam

“…Since the (S,W) value for Mg-implanted GaN with N-implantation was identical to that for N-implanted GaN (not shown), the same identification of the defect species can be done. This conclusion agrees with that obtained for Mg-implanted GaN with different implantation energies and implantation dosages [24][25][26]34 . After annealing at 1000 and 1100°C, the (S,W) shifted toward the right-hand side.…”

“…The trapping property of positrons by vacancy-type defects in Mg-implanted GaN was reported in previous works [24][25][26] . Annealing behaviors of vacancy-type defects for Mg-implanted GaN with [Mg] = 10 17 -10 19 cm −3 were reported in ref.…”

“…For unimplanted GaN, the S value at a low E (0.1 keV) was high, which was due to the annihilation of positrons at the surface. The S value saturated above E = 20 keV, which is due to the annihilation of positrons from the delocalized state in GaN [24][25][26] . Thus, the shoulders in the S-E curves for ion implanted GaN before annealing (E = 3-10 keV) can be attributed to the trapping of positrons by vacancy-type defects introduced by ion implantation.…”

“…Positron annihilation spectroscopy. Details on positron annihilation spectroscopy 22,23 and its application to Mg-implanted GaN are given elsewhere [24][25][26] . Using a monoenergetic positron beam, the Doppler broadening spectra of the annihilation radiation were measured as a function of the incident positron energy E by using two Ge detectors.…”

Optical Investigation of Proton‐Irradiated Metal Organic Chemical Vapor Deposition AlGaN/GaN High‐Electron‐Mobility Transistor Structures

“…Therefore, these two measurements indicate that higher dosage 2 MeV proton irradiation introduces a uniform distribution of trap centers (radiative and nonradiative recombination centers) across the bulk of the GaN‐buffer layer. Recently reported time‐resolved PL experiments combined with positron annihilation spectroscopy (PAS) measurements of H‐implanted GaN templates identified Ga‐vacancy‐related defects such as V Ga and V Ga V N as the major nonradiative centers in n‐type GaN . PAS experiments are planned on selected samples of our irradiated set to verify if V Ga ‐related defects are responsible for the large luminescence intensity quenching observed in our luminescence experiments.…”