Compensation of magnesium by residual carbon impurities in p-type GaN grown by MOCVD

The effect of carbon impurities on electrical resistivity of Mg doped GaN grown by metal organic chemical vapor deposition (MOCVD) was investigated. It was noted that when the growth rate increases or the growth pressure decreases, the resistivity of p-GaN increases and the quality of p-type conductivity of epitaxial GaN deteriorates. The intensity of yellow luminescence (YL) in photoluminescence (PL) spectra was strengthened at the same time. Due to the compensation effect of carbon impurities on magnesium, it makes a significant influence on the electrical resistivity in p-GaN. Carbon impurities may form deep donors, resulting in yellow luminescence (YL) in photoluminescence spectra and compensate Mg acceptors to increase the resistivity of p-GaN. Thus, the low resistivity p-type GaN films can be obtained only when we appropriately reduce growth rate and improve reaction chamber pressure to reduce the residual carbon impurity concentration.