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

The effect of Si doping on structural peculiarities and electro-physical pr operties of GaN epilayers has been investigated in the concentration range 10(18)-8 x 10(19) cm(-3). It has been found that the Si doping changes the stress relaxation mechanism in the GaN epilayer on Al2O3 substrate, reducin g the biaxial compressive stress in the layer, as well as varying domain si zes in the columnar structure and densities of both micropipes and of verti cal screw and edge dislocations along the c-axis. Simultaneously, the densi ty of misfit dislocations parallel to the interface has increased. These st ructural peculiarities have promoted an increase in mobility from 20 to 200 cm(2) V-1 s(-1) in the Si-doped epilayers. The carrier transport mechanism in the GaN epilayers is discussed. (C) 1999 Elsevier Science S.A. All righ ts reserved.