High Resolution Laplace Deep Level Transient Spectroscopy Studies of Shallow and Deep Levels in n-GaN

Deep Level Transient Spectroscopy (DLTS) and high resolution Laplace DLTS (LDLTS) have been used to distinguish the difference between electrically active point and extended defects in MOVPE-grown n-type GaN. Three dominant features are observed in the conventional DLTS spectrum, with energies in the region of 40meV, 550meV and 1.46eV. However, detailed examination with LDLTS shows that all these peaks consist of multiple emission rates. The low energy feature consists of three point defects closely spaced in energy, which are identified as ON, and Si-Ga. The feature at around 550meV is shown to be due to defects in the strain field of a dislocation, which is deduced because the activation energy is dependent upon DLTS fill pulse length. LDLTS of this peak shows a very complicated spectrum, also indicative of a system of defects in a dislocation strain field. When applied to the very deep level of 1.46eV, LDLTS shows multiple emission rates but they behave as point-defect like states.