Characteristics of Mg-doped GaN epilayers grown with the variation of Mg incorporation

Abstract

We have studied the growth characteristics of Mg-doped GaN epilayers grown by MOCVD with the variation of Cp 2Mg flow rate. To optimize the p-type conductivity. We investigated the dependence of acceptor concentration on the dopant source (Cp 2Mg) flow rate. The van der Pauw technique, double-crystal X-ray diffractometry (DCXRD) and photoluminescence (PL) were used to characterize their crystallographic, electrical and optical properties. As the incorporation of Mg in GaN epitaxy increases, the surface morphology and crystallinity of the layers become rough and worse because of the increase of lattice distortion due to the large difference of the atomic size between Ga and Mg. With the increase of Mg incorporation, the resistivity of the epilayers increases abruptly without discontinuity because of the increase of much Mg–H complex not cracked. So, it is possible to know that only the partial amount of Mg–H complex in the layers are unbound by annealing at a certain condition. In spite of the continuous increase of Mg incorporation, the hole concentration of the epilayers first increases and then decreases from a certain Mg flow rate. As well as the results of hole concentration, the blue emission intensity of the layers in PL spectra at room temperature first increases and then decreases from a certain Mg flow rate. Therefore, it can be concluded that there is a limitation in Mg activation and the hole concentration decreases from this limit though the incorporation of Mg increases.