Hole and interface traps in Mg-doped Al0.1Ga0.9N/GaN grown by metalorganic chemical vapor deposition

Deep level traps in Mg-doped Al0.1Ga0.9N/undoped GaN heterostructures grown by metalorganic vapor deposition with different Cp2Mg molar flow rates are studied by deep level transient spectroscopy (DLTS). Two distinct hole traps were observed, one with an activation energy of 0.18 eV (AD1) and the other with an activation energy of 0.88 eV (AD2) above the valence band maximum. From an analysis of the voltage dependence of DLTS spectra, the AD1 trap is associated with a defect in the Al0.1Ga0.9N/GaN interface based on the Poole-Frenkel model to interpret the enhancement of the thermal emission rate due to potential barrier lowering. The DLTS peak intensity of the AD2 trap steadily decreases with decreasing the Cp2Mg molar flow rate. It appears that the AD2 hole trap is strongly related to Mg-related deep levels, which contribute to the strong blue emission observed by photoluminescence measurements.