Control of passivation and compensation in Mg-doped GaN by defect quasi Fermi level control
Andrew Klump, Marc P. Hoffmann, Felix Kaess, James Tweedie, Pramod Reddy, Ronny Kirste, Zlatko Sitar, Ramón Collazo
Abstract
A defect quasi Fermi level (dQFL) control process based on above bandgap illumination was applied to control H and VN-complexes, which are the main contributors to the passivation and self-compensation, respectively, in Mg:GaN grown via metalorganic chemical vapor deposition. Secondary ion mass spectrometry measurements confirmed that the total Mg incorporation was unaffected by the process. However, the total H concentration was reduced to similar levels obtained by post-growth thermal activation prior to any annealing treatment. Similarly, the 2.8 eV emission in the photoluminescence spectra, attributed to compensating VN and its complexes, was reduced for the dQFL-process samples. After thermal activation and Ni/Au contact deposition, Hall effect measurements revealed lower resistivities (increased mobilities and free hole concentrations) for dQFL-grown samples with Mg doping concentrations above and below 2 × 1019 cm−3. All these results demonstrate that the dQFL process can effectively reduce the H-passivation and self-compensation of the Mg:GaN films.