Effects of Si-doping on characteristics of semi-polar (112Ì 2) plane Al0.45Ga0.55N epi-layers

The semi-polar (112̅2) plane Al0.45Ga0.55N epi-layers with various Si-doping levels were successfully deposited on (10-10) m-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD). And the effects of Si-doping on the characteristics of the epi-layer samples were studied extensively by high-resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM), Raman spectroscopy, and Hall effect measurements. The characterization results showed that the compressive strain in the as-deposited Al0.45Ga0.55N films could be completely relaxed by Si-doping with appropriate silane (SiH4) mole flow rate owing to the enhanced dislocation movements induced by Si dopants. This fact implies that Si-doping to the semi-polar (112̅2) plane Al0.45Ga0.55N epi-layer is especially beneficial to the interaction and annihilation of the dislocations, resulting in a significant improvement in crystal quality. Moreover, the minimum root mean square (RMS) detected by AFM was as small as 1.47 nm, and the electron concentration and mobility was determined by the Hall effect measurement to be 1.8×1019 cm−3 and 36.65 cm2 V−1 s−1 for the same sample, respectively.