Silicon doping of semipolar (112¯2)Al_xGa_1−xN(0.50≤x≤0.55)

The effect of silicon doping on the growth and properties of ∼1.0μm-thick Al_xGa_1-xN(0.50≤x≤0.55) layers grown on semipolar (112¯2)AlN templates by metalorganic vapour phase epitaxy was studied. The layers were grown with different disilane/group-III precursors ratios that varied from 2.8×10⁻⁵ to 3.4×10⁻⁴. The surface morphology of the Si-doped (112¯2)AlGaN layers showed undulations along [11¯00]_AlGaN,AlN with a root-mean square roughness of about 4.0 nm within a scan range of 20×20μm². Different photoluminescence peaks have been linked to negatively charged cation vacancies (V_III³⁻) and their complexes with impurities such as V_III³⁻-3O_N¹⁺, (V_III complex)¹⁻, and (V_III complex)²⁻. The optimised AlGaN:Si layer exhibited a carrier concentration of ∼1.2×10¹⁹ cm⁻³, a carrier mobility of 30.7 cm²/V s, and a resistivity of 0.018Ωcm, as determined by Hall-effect measurements at room temperature. A correlation between the resistivity and luminescence emission intensities of AlGaN near-band-edge and impurity-related complexes was found.