Properties of Si-doped a-plane AlGaN layers

The non-polar a-plane (11 (2) over bar0) n-type AlGaN epi-layers with high electron concentration were successfully grown on r-plane (1 (1) over bar 02) sapphire substrates by metal organic chemical vapor deposition. High-resolution X-ray diffraction, room temperature photoluminescence spectrum, and Hall effect measurement were used to examine the influence of Si-doping on the crystalline quality, and the optical and electrical characteristics of the non-polar a-plane n-AlGaN epi-layer, respectively. The characterization results indicate that the electron concentration (EC), the electron mobility, and the crystalline quality for the non-polar a-plane n-AlGaN epi-layers could be improved significantly by optimizing the epitaxial growth conditions, especially the mole flow rate of SiH4 in the Si-doping process. In fact, at a SiH4 mole flow rate of 10.2 nmol/min, an EC as high as 1.25 x 10(18) cm(-3) and an electron mobility up to 3.86 cm(2)/V were achieved with the non-polar n-AlGaN epi-layer sample with the Al content of 41%.