Mg-Doped Hexagonal InN/Al2O3 Films Grown by MBE

Abstract

We report on the first attempts of Mg doping of hexagonal InN/Al2O3(0001) films grown by plasma-assisted molecular beam epitaxy. A dramatic improvement of crystalline quality of InN : Mg epilayers has been observed at the magnesium concentration in the 1019 to 3 ×1020 cm—3 range as indicated by triple-crystal X-ray diffraction θ-rocking curve peak width below 30 arcsec. An increase of Mg doping higher than 1021 cm—3 deteriorates dramatically the InN crystal quality and surface morphology. A thermodynamic model of the surfactant Mg effect is proposed. The increase in Mg concentration causes the reduction by an order of magnitude (down to n = 1019 cm—3) of free electron concentration in InN : Mg layers compared to undoped ones, accompanied by a significant reduction of electron mobility. This behavior can be explained by a complex effect of the crystal quality improvement and the carrier compensation by incorporated Mg acceptors.