Comparative studies of polar (0001) and semipolar (112¯2) n-type GaN with different Si doping concentrations

We investigated the electrical and crystalline properties of polar (0001) GaN and semipolar (112¯2) n-type GaN with different Si doping concentrations grown on c-plane and m-plane sapphire substrates, respectively. Regardless of the polar and semipolar GaN, the electron concentrations of polar (0001) and semipolar (112¯2) GaN increased proportionally with increasing silane (SiH4) flow rates. However, the mobility of polar (0001) n-type GaN was decreased from 391 to 242 cm2/V s, whereas that of semipolar (112¯2) n-type GaN unexpectedly increased from 110 to 180 cm2/V s on increasing the SiH4 flow rate. The full width at half maximum of X-ray rocking curves of semipolar (112¯2) n-GaN decreased on increasing the SiH4 flow rate, whereas that of polar (0001) n-GaN slightly increased with increasing SiH4 flow rate. In addition, the crystal domain size of semipolar (112¯2) n-GaN increased with increasing SiH4 flow rate, which was contrary to the trend seen in polar (0001) n-GaN. Based on these results, we suggest that Si doping of semipolar (112¯2) n-GaN would improve the crystalline qualities of semipolar (112¯2) GaN, resulting in an increase in the electron mobility and concentration.

► We examine comparative studies of polar and semipolar n-type GaN. ► The mobility of semipolar n-GaN is increased with Si doping concentration. ► The mobility of polar n-GaN is decreased with Si doping concentration. ► The crystal properties of semipolar n-GaN are improved by Si doping. ► Si doping in semipolar GaN would improve crystal and electrical properties.