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

Very-high-quality p-type ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N/GaN}$ 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 $\text{x=26\%,}$ the hole concentration reaches a high value of ${\text{4.2×10}}^{18}\hspace{0.5em}{\mathrm{cm}}^{\text{−3}}$ 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.