Interface State Artefact in Long Gate-Length AlGaN/GaN HEMTs

Waller, William M.; Karboyan, Serge; Uren, Michael J.; Lee, Kean Boon; Houston, P.A.; Wallis, D. J.; Guiney, Ivor; Humphreys, C. J.; Kuball, Martin

doi:10.1109/ted.2015.2444911

Cited by 21 publications

(16 citation statements)

References 19 publications

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“…The real component of the admittance is the conductance, which when plotted as G ω against ω displays a characteristic peak for each V disc tested [11], as shown in Figure 2. The fitting algorithm used the logarithm of the ratio of the peak positions for the measured and model curves as the optimisation target to be minimised.…”

Section: Methodsmentioning

confidence: 99%

Ohmic Contact-Free Mobility Measurement in Ultra-Wide Bandgap AlGaN/AlGaN Devices

Butler

Waller

Uren

et al. 2018

IEEE Electron Device Lett.

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Section: Methodsmentioning

confidence: 99%

Ohmic Contact-Free Mobility Measurement in Ultra-Wide Bandgap AlGaN/AlGaN Devices

Butler

Waller

Uren

et al. 2018

IEEE Electron Device Lett.

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“…They reported an interface state density of 1 Â 10 12 cm À2 with an energy of 0.3 eV below the conduction band. Recently, Waller et al 30 showed that using the conductance method for extracting interface states is valid only for HEMTs with short gate length (L G < 10 lm). Utilizing this method for HEMTs with long gate lengths results in exaggerated interface state density.…”

Section: Charge States At the Algan-gan Interfacementioning

confidence: 99%

“…Utilizing this method for HEMTs with long gate lengths results in exaggerated interface state density. Waller et al 30 measured an interface state density of 5 Â 10 10 cm À2 in the Ga-polar GaN/AlGaN HEMTs which had gate lengths lower than 10 lm. The reason behind the formation of these interface states is not well-understood yet.…”

Section: Charge States At the Algan-gan Interfacementioning

confidence: 99%

“…Our calculations revealed that although decreasing the channel thickness or increasing the reverse gate bias in N-polar HEMTs increases interface roughness and alloy scattering rates, it is not significant enough to explain the severe reduction in the 2DEG mobility seen at room temperature (RT). We propose charged interface states (CIS) at the GaN-AlGaN interface 24,30 as the scattering mechanism responsible for the large reduction in the 2DEG mobility observed with decreasing channel thickness and/or increasing reverse gate bias in N-polar heterostructures. We also show that surface state dipoles (SSD) have a large effect in decreasing 2DEG mobility in thin channels where the dipoles are close to the 2DEG.…”

Section: Introductionmentioning

confidence: 99%

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Model to explain the behavior of 2DEG mobility with respect to charge density in N-polar and Ga-polar AlGaN-GaN heterostructures

Ahmadi

Keller

Mishra

2016

Journal of Applied Physics

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There are three possible ways of reducing the charge density (ns) in the N-polar high electron mobility transistors (HEMT) structures, by decreasing the channel thickness, applying reverse gate bias, or modifying the back-barrier. Understanding the behavior of 2DEG mobility as a function of ns is essential to design high performance HEMT devices. Experimental data show that in the N-polar HEMT structures, the 2DEG mobility reduces as the ns decreases by applying reverse gate bias or decreasing channel thickness, whereas in the Ga-polar HEMT structures, the 2DEG mobility increases as the ns in the channel decreases by applying reverse gate bias. In this paper, the 2DEG mobility as a function of ns is calculated in N-polar HEMTs for three different aforementioned cases, and is compared to that in the Ga-polar HEMT structures. It is shown that the conventional scattering mechanisms cannot explain these different behaviors. Two new scattering mechanisms, such as scattering from charged interface states and surface state dipoles (SSD), are introduced. It is revealed that in N-polar HEMT structures, reducing ns by applying reverse gate bias or decreasing channel thickness moves the charge centroid closer to the AlGaN-GaN interface. A combination of lower charge density (less screening of the scattering potential) and smaller distance between charge centroid and charged states at the interface leads to a severe mobility degradation in these cases. In contrast, reducing ns by modifying the back-barrier (decreasing back-barrier doping and/or decreasing AlGaN composition) in N-polar HEMT structures moves the charge centroid away from the interface. This behavior is similar to that in the Ga-polar HEMT structures. Therefore, in the last two mentioned cases, the 2DEG mobility first increases slightly as the ns decreases, and decreases slightly at very low charge densities. It is also shown that SSDs have large impact on the 2DEG mobility only in the N-polar (Ga-polar) HEMTs with thin channels (barriers).

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“…21,[25][26][27] The method reported by Yang et al 27 f -dispersions of the second slope onset (V ON ) in the ac-CV characteristics (Fig. 2), the interface-state density of LPCVD-SiN x /GaN-cap/AlGaN was calculated by…”

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confidence: 99%

Interface Si donor control to improve dynamic performance of AlGaN/GaN MIS-HEMTs

Song

Sun

et al. 2017

AIP Advances

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In this letter, we have studied the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with different interface Si donor incorporation which is tuned during the deposition process of LPCVD-SiNx which is adopted as gate dielectric and passivation layer. Current collapse of the MIS-HEMTs without field plate is suppressed more effectively by increasing the SiH2Cl2/NH3 flow ratio and the normalized dynamic on-resistance (RON) is reduced two orders magnitude after off-state VDS stress of 600 V for 10 ms. Through interface characterization, we have found that the interface deep-level traps distribution with high Si donor incorporation by increasing the SiH2Cl2/NH3 flow ratio is lowered. It’s indicated that the Si donors are most likely to fill and screen the deep-level traps at the interface resulting in the suppression of slow trapping process and the virtual gate effect. Although the Si donor incorporation brings about the increase of gate leakage current (IGS), no clear degradation of breakdown voltage can be seen by choosing appropriate SiH2Cl2/NH3 flow ratio.

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Interface State Artefact in Long Gate-Length AlGaN/GaN HEMTs

Cited by 21 publications

References 19 publications

Ohmic Contact-Free Mobility Measurement in Ultra-Wide Bandgap AlGaN/AlGaN Devices

Ohmic Contact-Free Mobility Measurement in Ultra-Wide Bandgap AlGaN/AlGaN Devices

Model to explain the behavior of 2DEG mobility with respect to charge density in N-polar and Ga-polar AlGaN-GaN heterostructures

Interface Si donor control to improve dynamic performance of AlGaN/GaN MIS-HEMTs

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