Fermi level effect on strain of Si doped GaN

摘要

Using high resolution X-ray diffraction and Hall effect measurements, we found that the tensile strain caused by dislocation inclination in Si doped GaN became immeasurable when carbon co-doping was used to compensate the free carriers. This result suggested that the tensile strain is related to free carrier concentration instead of Si concentration. Such an effect could be explained by the Fermi level effect on the dislocation climb at the growth surface mediated by Ga vacancies, whose concentration is strongly influenced by the Fermi level position. At a high electron carrier concentration, the formation energy of Ga vacancies is low and Ga vacancy concentration is high. Therefore, the dislocation climb-rate is enhanced, which results in a higher tensile strain. This phenomenon is similar to the well-known Fermi level effect on Ga vacancy governed diffusion in the GaAs system.