Effect of annealing time and pressure on electrical activation and surface morphology of Mg-implanted GaN annealed at 1300 °C in ultra-high-pressure nitrogen ambient

Abstract

We performed an isothermal annealing study on Mg-implanted GaN at 1300 °C in an ultra-high-pressure (1 GPa) nitrogen ambient. Annealing for more than 30 min resulted in a high acceptor activation ratio and a low compensation ratio that were comparable to those obtained with annealing at 1400 °C for 5 min. We also performed annealing at 1300 °C in a reduced nitrogen pressure of 300 MPa which makes us possible to expand the inner diameter of annealing equipment in the future. High electrical activation, similar to one obtained by annealing at 1 GPa, was successfully obtained.

Effect of Ultra‐High‐Pressure Annealing on Defect Reactions in Ion‐Implanted GaN Studied by Positron Annihilation

“…Recently, Sakurai and co-workers reported that the ultrahigh-pressure annealing (UHPA) process is effective for activating implanted p-type dopant (Mg). [14][15][16][17][18][19][20][21][22] In this process, Mg-implanted GaN is annealed at a high temperature (up to 1480 °C) under a high N 2 pressure (1 GPa) without forming a surface protection film on the sample. They reported that the activation rate of Mg exceeded 70% with UHPA, and the carrier mobility was close to that of epitaxial p-type GaN.…”

“…[14] Although these works have shown that UHPA is a promising postimplantation process, the formation of secondary defects, such as dislocations, precipitates, and stacking faults, was observed after annealing. [21,22] These defects could act as compensators of p-type dopant. For vertical power devices, the presence of such defects could show detrimental effects to the electric properties and the reliability of devices.…”

Effects of Hydrogen Incorporation on Mg Diffusion in GaN‐Doped with Mg Ions via Ultra‐High‐Pressure Annealing

“…Using this technique, the implantation-induced strain is effectively removed, [12] and high acceptor activation percentages greater than 80% respective to implanted magnesium (Mg) ions have been obtained. [10,13,14] Unfortunately, prolonged annealing at high temperatures can promote the diffusion of Mg atoms so that the dopant dispersion profile is changed. [10,[13][14][15] Sakurai et al [15] reported that the diffusion coefficient for Mg atoms in GaN was 30 times larger than that for Mg in epitaxially grown Mg-doped GaN.…”

“…[10,13,14] Unfortunately, prolonged annealing at high temperatures can promote the diffusion of Mg atoms so that the dopant dispersion profile is changed. [10,[13][14][15] Sakurai et al [15] reported that the diffusion coefficient for Mg atoms in GaN was 30 times larger than that for Mg in epitaxially grown Mg-doped GaN. This finding suggests that dopant diffusion is enhanced by the formation of point defects during implantation.…”

“…Using this technique, the implantation‐induced strain is effectively removed, [ 12 ] and high acceptor activation percentages greater than 80% respective to implanted magnesium (Mg) ions have been obtained. [ 10,13,14 ]…”