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The unique nature of built-in electric field induced positive/negative charge pairs of polar semiconductor heterojunction structure has led to a more realistic device model for hexagonal III-nitride HEMT. In this modeling approach, the distribution of charge carriers is dictated by the electrostatic potential profile instead of Femi statistics. The proposed device model is found suitable to explain peculiar properties of GaN HEMT structures, including: (1) Discrepancy in measured conventional linear transmission line model (LTLM) sheet resistance and contactless sheet resistance of GaN HEMT with thin barrier layer. (2) Below bandgap radiation from forward biased Nickel Schottky barrier diode on GaN HEMT structure. (3) GaN HEMT barrier layer doping has negligible effect on transistor channel sheet charge density. [ABSTRACT FROM AUTHOR]

We present a methodology and the corresponding experimental results to identify the exact location of the traps that induce hot electron trapping in AlGaN/GaN heterostructures grown on Si substrates. The methodology is based on a combination of lateral and vertical electrical stress measurements employing three ohmic terminals on the test sample structure with different GaN buffer designs. By monitoring the evolution of the lateral current during lateral as well as vertical stress application, we investigate the trapping/detrapping behaviors of the hot electrons and identify that the traps correlated with current degradation are in fact located in the GaN buffer layers. The trap activation energies (0.38-0.39 eV and 0.57-0.59 eV) extracted from either lateral or vertical stress measurements are in good agreement with each other, also confirming the identification. By further comparing the trapping behaviors in two samples with different growth conditions of an unintentionally doped GaN layer, we conclude that the traps are most likely in the unintentionally doped GaN layer but of different origins. It is suggested that the 0.38-0.39 eV trap is related to residual carbon incorporation while the 0.57-0.59 eV trap is correlated with native defects or complexes. [ABSTRACT FROM AUTHOR]

High-temperature transport properties in high-mobility lattice-matched InAlN/GaN heterostructures have been investigated. An interesting hysteresis phenomenon of the two dimensional electron gas (2DEG) density is observed in the temperature-dependent Hall measurements. After hightemperature thermal cycles treatment, the reduction of the 2DEG density is observed, which is more serious in thinner InAlN barrier samples. This reduction can then be recovered by light illumination. We attribute these behaviors to the shallow trap states with energy level above the Fermi level in the GaN buffer layer. The electrons in the 2DEG are thermal-excited when temperature is increased and then trapped by these shallow trap states in the buffer layer, resulting in the reduction and hysteresis phenomenon of their density. Three trap states are observed in the GaN buffer layer and CGa may be one of the candidates responsible for the observed behaviors. Our results provide an alternative approach to assess the quality of InAlN/GaN heterostructures for applications in high-temperature electronic devices. [ABSTRACT FROM AUTHOR]

A self-terminating gate recess wet etching technique with thermal oxidation of the AlGaN/GaN layer followed by etching in potassium hydroxide (KOH) solution was recently proposed by the present authors for normally-off AlGaN/GaN metal-oxide semiconductor field effect transistors (MOSFETs). In this present reported work, the oxidation process inside the AlGaN/GaN heterostructure involved in this technique was analysed using several material characterisation methods. The measurement results show that the concentration and depth of the O element distribution increase with increased thermal oxidation temperature. It is worth noting that after 650°C oxidation almost no O element could be found in the GaN layer and the O element mainly locates in the AlGaN layer with an obvious correlation between the distribution of Al and O elements, where the Al(Ga)-oxide was detected by X-ray photoelectron spectroscopy, which could be etched by 70°C KOH. Thus, self-terminating wet etching on the AlGaN/GaN material is achieved. [ABSTRACT FROM AUTHOR]