Role of Mg hole traps in hole transport of p-GaN/UID-GaN/AlGaN/GaN heterostructure

This work reports on the dynamics of hole transport in a p-GaN/UID-GaN/AlGaN/GaN heterostructure investigated through temperature-dependent I–V characteristics. The pronounced temperature and bias dependence of the sheet resistance reveal that bulk p-GaN dominates hole transport at higher bias. Arrhenius analysis of the sheet resistance confirms the presence of hole traps with a zero-field activation energy of 110 meV in the bulk p-GaN, attributed to two possible Mg-related states: the Mg–H complex and the MgGa acceptor. The bias dependence of the sheet resistance originates from the field-dependent lowering of the activation energy, explained by the Poole–Frenkel effect. At low bias, transport is impacted by tunneling of thermally activated holes across the Ru/p-GaN Schottky contact, described by reverse thermionic field emission (TFE). The bias-dependent reduction of contact resistance is consistent with this tunneling phenomenon. This behavior is ascribed to the reduction in Schottky barrier height (SBH), which follows a power law dependence on the voltage with an exponent m=0.41. The correlation comes from strong interfacial fields and field-induced hole activation at the reverse-biased interface.