Effects of the multi-step activation process on the carrier concentration of p-type GaN

•Hole concentration of p-GaN was enhanced by multi-step activation process.•The O2 plasma treatment is attributed to the enhanced hole concentration of p-GaN.•PL peak intensity was also enhanced by MS activation process.

A multi-step activation method, which include an oxygen plasma treatment, chemical treatment, and post annealing in N2 was proposed to enhance the hole concentration of a p-type GaN epitaxial layer. This process was found to effectively activate p-GaN by increasing the hole concentration compared to that of the conventionally annealed sample. After the optimal oxygen plasma treatment (10 min at a source and table power of 500 W and 100 W, respectively), followed by a HCl and buffered oxide etchant treatment, and then by a post-RTA process in a N2 environment, the hole concentration was increased from 4.0 × 1017 to 2.0 × 1018 cm−3. The oxygen plasma was found to effectively remove the remaining H atoms and subsequent wet treatment can effectively remove the GaOx that had formed during O plasma treatment, resulting in the higher intensity of photoluminescence.