The metal modulated epitaxy (MME) growth technique is reported as a reliable approach to obtain reproducible large hole concentrations in Mg-doped GaN grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates. An extremely Ga-rich flux was used, and modulated with the Mg source according to the MME growth technique. The shutter modulation approach of the MME technique allows optimal Mg surface coverage to build between MME cycles and Mg to incorporate at efficient levels in GaN films. The maximum sustained concentration of Mg obtained in GaN films using the MME technique was above 7×1020 cm−3, leading to a hole concentration as high as 4.5×1018 cm−3 at room temperature, with a mobility of 1.1 cm2 V−1 s−1 and a resistivity of 1.3 Ω cm. At 580 K, the corresponding values were 2.6×1019 cm−3, 1.2 cm2 V−1 s−1, and 0.21 Ω cm, respectively. Even under strong white light, the sample remained p-type with little change in the electrical parameters.
Burnham, S. D.,
Look, D. C.,
& Doolittle, W. A.
(2008). Reproducible Increased Mg Incorporation and Large Hole Concentration in GaN Using Metal Modulated Epitaxy. Journal of Applied Physics, 104 (2), 24902.