Guofeng Yang

Forward current transport mechanisms in Ni/Au-AlGaN/GaN Schottky diodes

The forward current transport mechanisms in Ni/Au-AlGaN/GaN Schottky diodes are studied by temperature dependent current-voltage (T-I-V) measurements from 298 to 473u2009K. The zero-bias barrier height qϕBn and ideality factor values determined based on the conventional thermionic-emission (TE) model are strong functions of temperature, which cannot be explained by the standard TE theory. Various transport models are considered to analyze the experimental I-V data. The fitting results indicate that the increased current at low bias is due to the trap-assisted tunneling with an effective trap density of about 8.8u2009×u2009106u2009cm−2, while the high-bias current flow is dominated by the TE transport mechanism, accompanied by a significant series resistance effect. By fitting the high-forward-bias I-V characteristics, the effective qϕBn values with a small negative temperature coefficient are obtained. The temperature dependence of the saturation tunneling current and qϕBn is finally explained by considering the thermall...

Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

Lattice-matched Pt/Au-In0.17Al0.83N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

A Comprehensive Study of Reverse Current Degradation Mechanisms in Au/Ni/n-GaN Schottky Diodes

In this paper, we perform a comprehensive study on the reverse current degradation mechanisms in Au/Ni/n-GaN Schottky diodes based on an in-depth understanding on the defect-related current transport mechanisms. Instead of traditional Poole–Frenkel (PF) emission model, an extended bulk-limited PF transport process, including the compensation effect, is adopted to explain the variation of the PF current slope as a function of the stress time, which majorly takes place inside the depletion region near the neutral semiconductor side. Based on the electrostatic analysis, we develop a shallow donor-like defects model to address the current degradation kinetics, which states that the energetic electrons produced by Fowler–Nordheim tunneling can induce significant Joule heating effect during the subsequent drift move of field, and give rise to the formation of the donor-like defects, and in turn enhance the surface electrical field to cause a significant increase of the tunneling component, in good agreement with the emission microscope observations.

Tunneling-Hopping Transport Model for Reverse Leakage Current in InGaN/GaN Blue Light-Emitting Diodes

The nature of charge transport in GaN-based light-emitting diodes (LEDs) under reverse biases still remains elusive as the bias- and temperature-dependent characteristics of the current can hardly be formulated using a single transport mechanism. In this letter, based on numerical fitting, we develop a combined tunneling-hopping transport model to describe the complete electrical characteristics of the reverse leakage current in InGaN/GaN blue LEDs. This model depicts that the current behaviors are majorly limited by the charge transport process through the depletion region near the neutral n-side, where electrons at the valance band are ready to tunnel into the unoccupied localized gap states in neighborhood near the electron quasi-Fermi level (<inline-formula> <tex-math notation=LaTeX>

Surface Acceptor-Like Trap Model for Gate Leakage Current Degradation in Lattice-Matched InAlN/GaN HEMTs

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Current and light emission efficiency behaviors in GaN-based LEDS

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Epitaxial growth and interfacial property of monolayer MoS2 on gallium nitride

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Hot electrons induced degradation in lattice-matched InAlN/GaN high electron mobility transistors

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GaN-based p-i-n ultraviolet photodetectors with a thin p-type GaN layer on patterned sapphire substrates

Typical leakage current degradation behaviors are observed in lattice-matched In0.17Al0.83N/GaN Schottky structure, suggesting that the inverse piezoelectric effect may not be the major mechanism causing gate degradation in the stress-free GaN HEMTs. The low-field current is dominated by Poole-Frenkel emission of electrons with the compensation effect, indicative of the presence of deep-level acceptor-like traps in the surface barrier layer. A new surface acceptor-like trap model is developed to address the degradation kinetics, emphasizing that the high-field Fowler-Nordheim tunneling process may cause the generation of the acceptor-like defects, which could in turn introduce a thinner surface barrier to enhance the tunneling component, and the corresponding threshold voltage should determine the critical voltage of gate degradation.

A Reusable and High Sensitivity Nitrogen Dioxide Sensor Based on Monolayer SnSe

Light emitting diodes (LEDs) with an InGaN/GaN multi-quantum wells structure have been fabricated. Their room temperature current-voltage characteristics and light emission efficiency behaviors under reverse-current stress and at different temperatures have been investigated. The forward current in the low-bias region is dominated by electron tunneling, while in the medium-bias region the heavy holes are the dominant tunneling entities. The reverse leakage current can be well explained with the defect-assisted tunneling model. The reverse-current stress induced additional structure defects in the active layer not only increase reverse-bias leakage current as leakage paths, but also degrade the overall efficiency of the LEDs as non-radiative recombination centers. The emission efficiency of the GaN-based LEDs is a strong function of temperature especially at low currents. With increasing temperature, the non-radiative recombination rate is enhanced at the extended structure defect, pushing the peak-efficiency current density toward the high current direction.