Dislocations and stacking faults in hexagonal GaN

We present experimental and theoretical results on extended defects of hexagonal GaN grown by metal organic vapour deposition (MOCVD). Transmission electron microscopy (TEM) measurements indicate the presence of 3 nm wide type I 1 stacking faults (SFs) related to the MOCVD growth, and 2― 4 nm SFs of unidentified type related to the ion implantation. We simulated infinite SFs of different types I 1 , I 2 and I 3 . First principles calculations were used to model Shockley partial dislocations, the core structure of the dislocations and intrinsic SFs. We estimate defect level positions and the formation energy of the infinite SFs. We also present results of the calculations and available experimental data on finite size SFs bounded by partial dislocations in wurtzite GaN. Calculation of the infinite SFs revealed shallow levels, but no deep levels. In the SFs bound by dislocations there are deep filled levels in the range of 0.4―0.8 eV from the valence band maximum (VBM) located at the atoms of the 90° dislocations. We also calculated the segregation of the C, n-dopant, Si or O and the p-dopant, Mg, to the dislocations and SFs. The effect of the segregation is found to be stronger for the SFs with partials. The results of the calculations are correlated with the experimental data on GaN obtained from high resolution TEM and Hall measurements. We suggest mechanisms of the formation of the SFs I 1 and I 2 after ion implantation and high temperature anneal and explain the difficulties of p-type doping with the formation of the extended defects.