High Si and Ge n-type doping of GaN doping - Limits and impact on stress

We report on GaN n-type doping using silane, germane, and isobutylgermane as Si and Ge dopants, respectively. A significant increase in tensile stress during growth is observed for Si doped samples while this is not the case for Ge doping. In addition, Ge can be doped up to 2.9 x 10(20) cm(-3), while Si doping leads to 3-D growth already at concentrations around 1.9 x 10(19) cm(-3). The free carrier concentration was determined by Hall-effect measurements, crystal quality, and structural properties by x-ray diffraction measurements. Additionally, secondary ion mass spectroscopy and Raman measurements were performed demonstrating the high material quality of Ge doped samples. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3695172]