Depth Analyses of Mg‐Acceptor and Si‐Donor Concentrations in GaN by Combining Stepwise Etching and Photoluminescence

Abstract

The depth profiles of the Mg‐acceptor or Si‐donor concentration in GaN are visualized using stepwise etching and photoluminescence (PL) measurements. Low‐damage etching techniques are applied: multistep‐bias inductively coupled plasma reactive ion etching for p‐type GaN and electrochemical etching for n‐type GaN. To determine the concentration calibration curve, the PL intensity ratios of Mg‐neutral acceptor or Si‐neutral donor‐bound excitons to free excitons are plotted against Mg or Si atomic concentrations in etched GaN epitaxial layers having depth distributions of dopant concentrations, as estimated by secondary ion mass spectrometry. The quantitative accuracy of the calibration curve is ensured by the appropriate sample temperature and excitation density ranges for PL. The stepwise dry etching and the Mg acceptor quantification by PL using this calibration curve are applied to Mg‐ion‐implanted GaN after ultra‐high‐pressure annealing at 1300 °C for 1 min. The obtained depth profile of the Mg‐acceptor concentration is consistent with the Mg atomic concentration profile in the region deeper than the implantation peak, whereas the acceptor concentration in the shallow region is lower than the Mg atomic concentration. This analysis is useful for revealing the site substitution ratio of dopants in GaN materials partially involving inactive dopants.