Investigation of Be diffusion coefficients for various crystallographic directions in GaN grown by HVPE

Diffusion of Be was investigated for the main crystallographic directions in HVPE-GaN: c [0001], m [10-10], and a [11-20]. Be was implanted into the samples at room temperature with a dose of 2.9e15 cm-2 with energy of 200 keV. Ultra-high pressure annealing (UHPA) was performed to repair the post-implantation damage and activate the dopant. The annealing was performed at different time (15 and 30 minutes) and temperature (1200 – 1400°C). Depth profiles of Be were measured by secondary ion mass spectrometry (SIMS). Diffusion coefficients were calculated using the complementary error function (erfc) or Boltzmann-Matano analysis. The determined diffusion coefficients were summarized in an Arrhenius plot: D(1/T). From this relation the pre-exponential factor D0 and the activation energy were calculated. In addition, it was possible to calculate the formation energy for interstitial Be as well as gallium vacancy defects.