Barrier heights of Schottky contacts on strained AlGaN/GaN heterostructures: Determination and effect of metal work functions

Lin, Zhaojun; Lu, Wu; Lee, Jaesun; Liu, Dongmin; Flynn, J. S.; Brandes, George R.

doi:10.1063/1.1584077

Cited by 81 publications

(37 citation statements)

References 12 publications

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“…10. Interestingly, the sum of the activation energy of TP1 (0.74 eV) and DP1 (0.57 eV) is close to the Schottky barrier height (1.27 eV) [37]. This suggests that this trap is inside the AlGaN barrier and is generally consistent with the overall picture in Figs.…”

Section: B Detrapping Behaviorsupporting

confidence: 78%

A Current-Transient Methodology for Trap Analysis for GaN High Electron Mobility Transistors

Joh

Alamo

2011

IEEE Trans. Electron Devices

378

245

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Abstract-Trapping is one of the most deleterious effects that limit performance and reliability in GaN HEMTs. In this paper, we present a methodology to study trapping characteristics in GaN HEMTs that is based on current-transient measurements. Its uniqueness is that it is amenable to integration with electrical stress experiments in long-term reliability studies. We present the details of the measurement and analysis procedures. With this method, we have investigated the trapping and detrapping dynamics of GaN HEMTs. In particular, we examined layer location, energy level, and trapping/detrapping time constants of dominant traps. We have identified several traps inside the AlGaN barrier layer or at the surface close to the gate edge and in the GaN buffer.

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Section: B Detrapping Behaviorsupporting

confidence: 78%

A Current-Transient Methodology for Trap Analysis for GaN High Electron Mobility Transistors

Joh

Alamo

2011

IEEE Trans. Electron Devices

378

245

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“…9 and 10, the H 2 O/H 2 redox couple forms a surface trapping state with an energy level around 0.5 eV above the Fermi level of the AlGaN/GaN HEMTs in equilibrium, which is also equivalent to around 0.5-0.6 eV below the AlGaN conduction band if we assume the Schottky barrier height is 1.0-1.1 eV. 20 This 0.5 eV energy difference is consistent with the activation energy that has been widely observed for the surface trapping states in AlGaN/GaN HEMTs, 21 which makes water molecules important candidates to explain the origin of electron trapping states on III-Nitride surface.…”

Section: Hypothesis For the Origin Of Current Collapse In Gan-basmentioning

confidence: 99%

On the redox origin of surface trapping in AlGaN/GaN high electron mobility transistors

Gao¹,

Chen²,

Tuller³

et al. 2014

Journal of Applied Physics

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Water-related redox couples in ambient air are identified as an important source of the surface trapping states, dynamic on-resistance, and drain current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). Through in-situ X-ray photoelectron spectroscopy (XPS), direct signature of the water-related species—hydroxyl groups (OH) was found at the AlGaN surface at room temperature. It was also found that these species, as well as the current collapse, can be thermally removed above 200 °C in vacuum conditions. An electron trapping mechanism based on the H2O/H2 and H2O/O2 redox couples is proposed to explain the 0.5 eV energy level commonly attributed to the surface trapping states. Finally, the role of silicon nitride passivation in successfully removing current collapse in these devices is explained by blocking the water molecules away from the AlGaN surface.

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“…A decrease in 2-DEG density leads to an increase in SBH, provided the polarization sheet charge density at the surface is unaffected [24]. Hence, a reduction in SBH will be caused by an increase in charge density due to the increase in the biaxial tensile stress.…”

Section: Mechanical Stressmentioning

confidence: 99%

Impact of Al<sub>2</sub>O<sub>3</sub> Passivation on AlGaN/GaN Nanoribbon High-Electron-Mobility Transistors

Joglekar

Adnane

Jones

et al. 2016

IEEE Trans. Electron Devices

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Passivation films are used in III-nitride (III-N) based devices to suppress current collapse and improve frequency performance. Several passivation films and deposition methods have the added effects of increasing the dc ON-and OFF-state currents in devices. In this paper, the physical mechanisms behind this current increase have been studied in both nanoribbon and planar devices with atomic-layer deposited Al 2 O 3 passivation. Increased tensile stress in the AlGaN layer due to passivation leads to an increase in the charge density in nanoribbon devices. Simultaneously, the mobility in nanoribbons increases after Al 2 O 3 passivation. These effects lead to a large (∼118%) increase in the saturation drain current in nanoribbon devices. In contrast, fixed positive charge at the Al 2 O 3 -AlGaN interface leads to a small (∼6%) saturation drain current increase in planar devices. In addition, the mechanisms behind the increase in the OFFstate drain current in the passivated devices are investigated. Schottky barrier lowering and the increase in surface and buffer conduction are found to be the major causes for the OFF-state current increase with passivation.

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Barrier heights of Schottky contacts on strained AlGaN/GaN heterostructures: Determination and effect of metal work functions

Cited by 81 publications

References 12 publications

A Current-Transient Methodology for Trap Analysis for GaN High Electron Mobility Transistors

A Current-Transient Methodology for Trap Analysis for GaN High Electron Mobility Transistors

On the redox origin of surface trapping in AlGaN/GaN high electron mobility transistors

Impact of Al<sub>2</sub>O<sub>3</sub> Passivation on AlGaN/GaN Nanoribbon High-Electron-Mobility Transistors

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