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

Akira Uedono,Shoji Ishibashi,Kohei Shima,Shinya Takashima,Kazunobu Kojima,Katsunori Ueno,Masaharu Edo,Ryo Tanaka,Shigefusa F Chichibu

doi:10.1038/s41598-021-00102-2

Abstract

A process for activating Mg and its relationship with vacancy-type defects in Mg-implanted GaN were studied by positron annihilation spectroscopy. Mg+ ions were implanted with an energy of 10 keV, and the Mg concentration in the subsurface region (≤ 50 nm) was on the order of 1019 cm−3. After the Mg-implantation, N+ ions were implanted to provide a 300-nm-deep box profile with a N concentration of 6 × 1018 cm−3. From capacitance–voltage measurements, the sequential implantation of N was found to enhance the activation of Mg. For N-implanted GaN before annealing, the major defect species were determined to Ga-vacancy related defects such as divacancy. After annealing below 1000 °C, the clustering of vacancies was observed. Above 1200 °C annealing, however, the size of the vacancies started to decrease, which was due to recombinations of vacancy clusters and excess N atoms in the damaged region. The suppression of vacancy clustering by sequential N-implantation in Mg-implanted GaN was attributed to the origin of the enhancement of the Mg activation.

Highlights

The ultra-high-pressure annealing (UHPA) process was applied to Mg-implanted Gallium nitride (GaN), and it was confirmed that high-temperature annealing (1300–1480 °C) under ultra-high N2 pressure (1 GPa) was effective at activating implanted Mg in GaN10,14,15. These works reported that the activation rate of Mg exceeded 70%, and the carrier mobility was close to that of epitaxial p-type GaN with the same doping concentration. These results suggest that the UHPA process is a promising post-implantation process, several technical issues, such as the inclusion of impurities, costs, throughput, etc., must be overcome for industrial applications of UHPA
We used positron annihilation to study the enhancement of Mg activation and its relationship to vacancy-type defects in Mg-implanted GaN with N-implantation
The observed enhancement of Mg activation was attributed to the suppression of vacancy clustering by sequential N-implantation

Summary

Introduction

A process for activating Mg and its relationship with vacancy-type defects in Mg-implanted GaN were studied by positron annihilation spectroscopy. Mg atoms diffuse in damaged regions introduced by ion implantation, and they interact with various defects such as vacancies and interstitials.

Results

Conclusion