Author:

Keywords:

InGaN, III-Nitrides, epitaxy, molecular beam epitaxy, Mg doping

Abstract:

Single crystalline InxGa1-xN (InGaN) shows interesting electrical and optical properties. The ability to tune the direct band gap by changing the alloy composition is promising for solar matched photovoltaics. Better understanding of the growth processes is required to improve the structural and optoelectronic properties. In this work we investigate the influence of Mg on the structural quality of InGaN layers grown by metal modulated epitaxy (MME). We will show that Mg doping in combination with the MME method can be used to improve the structural quality of InGaN layers. Mg is known to have a significant influence on the growth process by changing the growth mode [Monroy E et al., Appl. Phys. Lett. 84, 2554 (2004)], introducing compensating defects, and even changing the polarity. Transmission electron microscopy shows the presence of nano-sized inclusions of zinc blende structure in the wurtzite GaN matrix at the InGaN-GaN interface. The amount of zinc blende regions decreases significantly for InGaN deposition in the presence of Mg flux, which results in improved crystalline quality of the InGaN layers. The full width half maximum (FWHM) of the (0002) X-ray diffraction (XRD) peak is significantly reduced from 1105 arc sec to 356 arc sec. Our results indicate that Mg can be beneficial for the structural quality of InGaN grown on GaN and that the Mg acts as a surfactant for InGaN epitaxy or stimulates desorption of surface contamination.