Raman scattering characterization of p‐type AlGaN layers

Mg-doped Al x Ga 1-x N layers were characterized by microscopic Raman scattering to study the activation process of dopant by thermal annealing and behavior of H impurities. Two types of samples, a monolayer and a device-like (laser diode) structure, were prepared for this study. Local vibrational modes (LVMs) related to H and Mg were clearly observed in the monolayer sample. The LVMs evidenced activation of Mg in Ga site with the release of H. Electronic Raman signal due to free hole was also observed in the annealed sample. In the device-like structure sample, the Mg-doped Al x Ga 1- x N clading layer showed similar results, though the signal was weaker than the monolayer sample. Interactions with neighboring layers may have influenced the layer properties. Composition of Al in the Al x Ga 1-x N layer was also determined from phonon frequencies in both samples, and the result well agreed with that of X-ray diffraction analysis.