Highly Mg-doped GaN thin film grown by RF plasma-assisted molecular beam epitaxy

In this paper, we present the study of the electrical, structural and optical properties of p-type GaN grown on sapphire by RF plasma-assisted molecular beam eapitaxy (RF-MBE). Hall effect measurement shows that the film was highly doped with carrier concentration of 6.58 x 10(18) cm(-3). X-ray diffraction (XRD) measurement reveals that the GaN was epitaxially grown on sapphire substrate. For the photoluminescence (PL) measurement, a sharp and intense peak at 363.8 nm indicates that the sample is of high optical quality. The presence of the peak at 658.4 cm(-1) in Raman measurement confirmed that our p-type GaN sample was highly doped with Mg. Low resistance ohmic contacts on p-type GaN utilizing Ni/Ag metallization were fabricated and characterized. A good ohmic contact with a specific contact resistance as low as 8.5 x 10(-3) Omega cm(2) was achieved without any annealing treatments.