Effect of Si doping on structural, photoluminescence and electrical properties of GaN

The effect of Si doping on structural peculiarities and electro-physical properties of GaN epilayers has been investigated in the concentration range 1018–8×1019 cm−3. It has been found that the Si doping changes the stress relaxation mechanism in the GaN epilayer on Al2O3 substrate, reducing the biaxial compressive stress in the layer, as well as varying domain sizes in the columnar structure and densities of both micropipes and of vertical screw and edge dislocations along the c-axis. Simultaneously, the density of misfit dislocations parallel to the interface has increased. These structural peculiarities have promoted an increase in mobility from 20 to 200 cm2 V−1 s−1 in the Si-doped epilayers. The carrier transport mechanism in the GaN epilayers is discussed.