Role of the AlGaN Cap Layer on the Trapping Behaviour of N-Polar GaN MISHEMTs

Chiocchetta, Francesca; Calascione, C.; Santi, Carlo De; Sharma, Cristian; Rampazzo, F.; Zheng, Xiaoting; Romanczyk, Brian; Guidry, Matthew; Li, H.; Keller, S.; Mishra, Umesh K.; Meneghesso, Gaudenzio; Meneghini, Matteo; Zanoni, Enrico

doi:10.1109/irps46558.2021.9405111

Cited by 4 publications

(2 citation statements)

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“…In fact, N-polar GaN offers a much wider design space with respect to the Ga-polar counterpart. In N-polar devices [23], [24], [25], [65], [66], [67], [68], [69], [70], [71], [72], the AlGaN barrier layer is placed below the GaN channel layer and the 2DEG is formed between the gate contact and the (Al)GaN heterointerface. As a consequence, the distance between the 2DEG and the gate can be reduced without affecting AlGaN thickness and channel conductivity, thus achieving a better channel control and a higher transconductance.…”

Section: Short-channel Effects In Gan Hemtsmentioning

confidence: 99%

“…We tested N-polar MISHEMTs adopting the process described in [84]. A thin (2.6 nm) AlGaN cap layer was placed on top of the u. to be due to a positive threshold voltage shift [71], [72]; the amount of degradation is independent of the gate length in the 80-100-nm range. The activation energy of the threshold voltage recovery transient is 0.7 eV for all Al concentrations: the same trap located under the gate is responsible for CC; trapped charge and CC are originated by the gate leakage current.…”

Section: Deep-level Effects In N-polar Mishemtsmentioning

confidence: 99%

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Microwave and Millimeter-Wave GaN HEMTs: Impact of Epitaxial Structure on Short-Channel Effects, Electron Trapping, and Reliability

Zanoni,

De Santi,

Gao

et al. 2024

IEEE Trans. Electron Devices

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Application of gallium nitride high-electronmobility transistors (GaN HEMTs) to millimeter-wave power amplifiers requires gate length scaling below 150 nm: in order to control short-channel effects, the gate-to-channel distance must be decreased, and the device epitaxial structure has to be completely redesigned. A high 2-D electron gas (2DEG) carrier density can be preserved even with a very thin top barrier layer by substituting AlGaN with AlN, InAl(Ga)N, or ScAlN. Moreover, to prevent interaction of hot electrons with compensating impurities and defects in the doped GaN buffer, the latter has to be separated from the channel by a back barrier. Other device designs consist in adopting a graded channel (which controls the electric field) or to adopt nitrogen-polar (N-polar) GaN growth (which decreases the distance between gate and channel, thus attenuating short-channel effects). The aim of this article is to review the various options for controlling short-channel effects, improve off-state characteristics, and reduce drain-source leakage current. Advantages and potential drawbacks of each proposed solution are analyzed in terms of current collapse (CC), dispersion effects, and reliability.

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