| GaN is a wide gap semiconductor that has already been shown to be highly suitable for light emitting diodes and lasers in the UV-blue-visible spectrum and that shows great promise for microelectronic devices. However, the efficiency of these devices can be very dependent on the electrically active defects present in the material. These defects can generate deep levels within the otherwise forbidden bandgap that can act as carrier traps as well as recombination-generation centers. The aim of this work has been to characterize these deep levels throughout the bandgap of n-GaN grown by metal organic chemical vapor deposition (MOCVD) using deep level transient and optical spectroscopies.; The deep level spectrum of MOCVD-grown n-GaN presents traps at E c-Et = 0.58, 0.61, 1.35, 2.64-2.80, 3.04 and 3.22 eV, with concentrations varying from 1013 to 1016 cm −3. In general, changes in the concentrations of all these deep levels are not followed by equivalent changes in the TD density, suggesting a point defect origin for all these levels. Indeed, the 0.58 and 1.35 eV are found to be directly related to point defects or complexes of point defects, since they are highly passivated by hydrogen incorporation but no changes are found in the electrical activity of the threading dislocation (TD)-related regions. Moreover, one or both of these deep levels behaves as a recombination-generation center, indicating that point defects likely play a role in current leakage in n-GaN devices. The 2.64-2.80 eV band of states behaves both as an electron and hole traps. Moreover, its behavior under hydrogenation indicates that it is most likely related to VGa3− (V Ga-H)2− and (VGa-H2)− complexes. This band of states shows the carrier capture kinetics of an ideal extended defect, and thus is most likely found decorating the TDs. Hence, it may be responsible for current leakage and carrier trapping properties conventionally assigned to these extended defects. Finally, the 3.22 eV level has been found to be related to extrinsic MgGa point defects that arise as a result of diffusion of residual Mg found in the growth reactor, an element that is commonly used as a p-type dopant. |
