Characteristics of high-quality p-type AlxGa1−xN/GaN superlattices

Very-high-quality p-type AlxGa1−xN/GaN superlattices have been grown by low-pressure metalorganic vapor-phase epitaxy through optimization of Mg flow and the period of the superlattice. For the superlattice with x=26%, the hole concentration reaches a high value of 4.2×1018 cm−3 with a resistivity as low as 0.19 Ω cm by Hall measurement. Admittance spectroscopy was performed in order to investigate the electrical properties of the superlattices. These measurements confirm that superlattices with a larger period and higher Al composition have higher hole concentration and lower resistivity, as predicted by theory.