Observations regarding deep-level states causing p-type doping in AlTiO gate and positive threshold voltage shift in AlGaN/GaN high electron mobility transistors

Dutta Gupta, S and Joshi, V and Roy Chaudhuri, R and Shrivastava, M (2021) Observations regarding deep-level states causing p-type doping in AlTiO gate and positive threshold voltage shift in AlGaN/GaN high electron mobility transistors. In: Journal of Applied Physics, 130 (1).

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Abstract

Application of ternary oxides has emerged as a potential enabler to achieve enhancement mode (normally-OFF) operation in AlGaN/GaN high electron mobility transistors (HEMTs). However, it is not well understood what leads to the 2-Dimensional Electron Gas depletion or positive threshold voltage shift by the integration of these oxides in the gate stack. In this work, an electro-optical experiment-based method is used to probe the underlying mechanism. For experiments, AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors with gate stack consisting of AlTiO (ternary p-type oxide), (undoped binary oxides), and NiO (conventional p-type oxide) are used. Optical exposure with wavelengths falling in the UV regime (365�nm) was found to induce a negative threshold voltage shift in AlTiO based devices. Experimentation on different GaN buffer stacks, different gate oxides, and selective UV exposure only to the gate region established the phenomenon to be governed by properties of the ternary oxide. This was further confirmed by the fact that the negative threshold voltage shift with UV exposure was proportional to the positive shift achieved as a function of Al in AlTiO. The negative shift was found to be due to de-ionization of deep-level negative states in AlTiO, which resulted from the presence of Al at Ti sites. These negatively ionized deep-level states at room temperature result in p-type doping of the oxide, leading to the positive threshold voltage shift in AlTiO gate based HEMTs when compared with HEMTs with as gate oxide. © 2021 Author(s).

Item Type:	Journal Article
Publication:	Journal of Applied Physics
Publisher:	American Institute of Physics Inc.
Additional Information:	The copyright for this article belongs to American Institute of Physics Inc.
Keywords:	Aluminum gallium nitride; Computer circuits; Electron gas; Electron mobility; Electrons; Gallium nitride; Gates (transistor); III-V semiconductors; Ionization of gases; Logic gates; Magnetic semiconductors; Metals; MOS devices; Nickel oxide; Oxide semiconductors; Semiconductor doping; Threshold voltage; Titanium compounds; Transistors; Wide band gap semiconductors, 2-dimensional electron gas; Algan/gan high electron-mobility transistors; Electro-optical; Enhancement modes; Metal-oxide-semiconductor high electron mobility transistor; Negative shift; Positive shift; Threshold voltage shifts, High electron mobility transistors
Department/Centre:	Division of Electrical Sciences > Electronic Systems Engineering (Formerly Centre for Electronic Design & Technology)
Date Deposited:	09 Dec 2021 09:29
Last Modified:	09 Dec 2021 09:29
URI:	http://eprints.iisc.ac.in/id/eprint/69596

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