The dependence of barrier height inhomogeneity on the gate metal has been investigated for the AlGaN/GaN Schottky diode. The analysis from the electroreflectance spectroscopy measurement for different types of Schottky gate metals tried (in this case, Au, Pt, Pd, and Ni) reveals that the surface donor states of AlGaN/GaN heterostructure strongly depends on the type of Schottky gate metals used, which suggests that barrier height inhomogeneity is strongly dependent on the gate metal. The X-ray photoelectron spectroscopy also reveals a strong correlation between the barrier height inhomogeneity and the gate metal type.

Abstract-We propose a new method which can extract the information about the electronic traps in the semi-insulating GaN buffer of AlGaN/GaN heterostructure field-effect transistors (HFETs) using a simple test structure. The proposed method has a merit in the easiness of fabricating the test structure. Moreover, the electric fields inside the test structure are very similar to those inside the actual transistor, so that we can extract the information of bulk traps which directly affect the current collapse behaviors of AlGaN/GaN HEFTs. By applying the proposed method to the GaN buffer structures with various unintentionally doped GaN channel thicknesses, we conclude that the incorporated carbon into the GaN back barrier layer is the dominant origin of the bulk trap which affects the current collapse behaviors of AlGaN/GaN HEFTs.Index Terms-AlGaN/GaN HFET, semi-insulating GaN buffer, bulk trap, carbon-doped GaN back barrier

The dependence of the gate leakage mechanism in the AlGaN/GaN Schottky diode on the metal–semiconductor (MS) interface state has been investigated. Schottky gates with Au, Pt, Pd, and Ni showed the remarkably different gate leakage mechanisms in the reverse direction. Through the analysis of the temperature dependent reverse leakage currents, it is shown that the discrete energy levels of MS interface states are the key factor in determining whether the leakage mechanism at the high temperature over 300 K is caused by the electron tunneling or by the Frenkel–Poole emission from the MS interface state to the conductive dislocation state.