Backward diodes using heavily Mg-doped GaN growth by ammonia molecular-beam epitaxy

We grew heavily Mg-doped GaN using ammonia molecular-beam epitaxy. The use of low growth temperature (740 °C) allows decreasing the incorporation of donor-like defects (<3 × 1017 cm−3) responsible for p-type doping compensation. As a result, a net acceptor concentration of 7 × 1019 cm−3 was achieved, and the hole concentration measured by Hall effect was as high as 2 × 1019 cm−3 at room temperature. Using such a high Mg doping level, we fabricated GaN backward diodes without polarization-assisted tunneling. The backward diodes exhibited a tunneling-current density of 225 A/cm2 at a reverse bias of −1 V at room temperature.