Thermoelectric enhancement in the two-dimensional electron gas of AlGaN/GaN heterostructures

Nagase, Kazuya; Takado, S.; Nakahara, Ken

doi:10.1002/pssa.201532653

Cited by 10 publications

(5 citation statements)

References 21 publications

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“…Theoretically calculated S of electron‐doped GaN with a parabolic‐shaped energy dependence of DOS around the conduction band bottom ( T = 300 K). Experimentally obtained values, which are reported by Sztein et al, Brandt et al, and Nagase et al, are plotted for comparison. Calculated line completely reproduces these reported values.…”

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confidence: 99%

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High Thermoelectric Power Factor of High‐Mobility 2D Electron Gas

et al. 2017

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Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower (S), high electrical conductivity (σ), and low thermal conductivity (κ). State‐of‐the‐art nanostructuring techniques that significantly reduce κ have realized high‐performance thermoelectric materials with a figure of merit (ZT = S 2∙σ∙T∙κ−1) between 1.5 and 2. Although the power factor (PF = S 2∙σ) must also be enhanced to further improve ZT, the maximum PF remains near 1.5–4 mW m−1 K−2 due to the well‐known trade‐off relationship between S and σ. At a maximized PF, σ is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal‐oxide‐semiconductor high electron mobility transistor (MOS‐HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS‐HEMT simultaneously modulates S and σ of the high‐mobility electron gas from −490 µV K−1 and ≈10−1 S cm−1 to −90 µV K−1 and ≈104 S cm−1, while maintaining a high carrier mobility (≈1500 cm2 V−1 s−1). The maximized PF of the high‐mobility electron gas is ≈9 mW m−1 K−2, which is a two‐ to sixfold increase compared to state‐of‐the‐art practical thermoelectric materials.

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confidence: 99%

“…We used 0.19 m 0 as m * of GaN, where m 0 is the free electron mass. Figure shows the calculated S of bulk GaN as a function of the volume carrier concentration ( n v ) at 300 K. For comparison, several reported S values of electron‐doped GaN are also plotted (Brandt, Sztein, Nagase). The calculated line completely reproduces these reported values.…”

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confidence: 99%

High Thermoelectric Power Factor of High‐Mobility 2D Electron Gas

et al. 2017

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“…Only a few studies can be found on their thermoelectric behaviour as their application in the thermoelectric field has not yet been developed. [7][8][9][10][11] In this study, we measure the electrical properties and Seebeck coefficient of n-type GaN and an AlGaN/GaN 2DEG.…”

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confidence: 99%

Thermoelectric Properties of n-type GaN and 2D Electron Gas in AlGaN-GaN Heterostructure

Bryan

Faucherand

Charles

et al. 2021

Journal of Elec Materi

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In this paper, the thermoelectric properties of n-type GaN and a 2D electron gas (2DEG) created from an AlGaN/GaN heterostructure are presented. Their thermoelectric properties are essential in order to optimise the thermoelectric devices they are used for, such as thermoelectric sensors, generators or coolers. In this study, Seebeck coefficients of À 162 lV/K and À 86 lV/K and power factor (rS 2) values of 0.56 mW/(m K 2) and 3.1 mW/(m K 2) were obtained for ntype GaN and the AlGaN/GaN heterostructure, respectively, at 430 K. Their Seebeck coefficient and resistivity were also measured over a number of temperature cycles, with no change in either of these measurements during the cycling, implying that these materials are thermoelectrically stable. Seebeck coefficients and thermoelectric properties of both materials remain stable throughout the temperature changes. These characteristics show the suitability of these materials for high performance thermoelectric sensors.

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“…Among those methods to realize large thermoelectric power factor in thin film/substrate, interface engineering has been proven to be an effective approach to enhance Seebeck effect of the heterostructure. Especially, the presence of quasitwo-dimensional electron gas (quasi-2DEGs) at the interface provides a dominant contribution to the enhancement of |S| 1,[16][17][18][19] . As an ideal substrate with unique structure, physical and chemical properties, SrTiO3 (STO) has been widely applied in thin film growth as well as the exploration of novel lowdimensional physics 1,[20][21][22][23][24][25] .…”

Section: Introductionmentioning

confidence: 99%

Excellent thermoelectric performance of ZrTe2 thin films and device

Suen

Cai

et al. 2021

Preprint

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Achieving high thermoelectric power factor in thin film heterostructures is essential for integrated and miniatured thermoelectric device applications. In this work, we demonstrate a mechanism and device performance of enhanced thermoelectric power factor through coupling the interfacial confined two-dimensional electron gas (2DEG) with thin film conductivity in a transition metal dichalcogenides-SrTiO3 heterostructure. Owing to the formed conductive interface with two-dimensional electron confinement effect and the elevated conductivity, the ZrTe2/SrTiO3 (STO) heterostructure presents enormous thermoelectric power factor as high as 4×10^5 μW/cmK^2 at 20 K and 4800 μW/cmK^2 at room temperature. Formation of quasi-two-dimensional electrons gas at the interface is attributed to the giant Seebeck coefficient, and enhanced electrical conductivity is suggested to be originated from charge transfer induced doping in the ZrTe2, which leads to extremely large thermoelectric power factor. By taking the thermal conductivity of STO substrate as a reference, the effective zT value of this heterostructure can reach 1.5 at 300 K. This high thermoelectric figure of merit is demonstrated by a prototype device based on this heterostructure which results in 3K temperature cooling by passing through a current of 100 mA. This superior thermoelectric property makes this heterostructure a promising candidate for future thermoelectric device, and more importantly, paves a new pathway to design promising high-performance thermoelectric systems.

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Thermoelectric enhancement in the two-dimensional electron gas of AlGaN/GaN heterostructures

Cited by 10 publications

References 21 publications

High Thermoelectric Power Factor of High‐Mobility 2D Electron Gas

High Thermoelectric Power Factor of High‐Mobility 2D Electron Gas

Thermoelectric Properties of n-type GaN and 2D Electron Gas in AlGaN-GaN Heterostructure

Excellent thermoelectric performance of ZrTe2 thin films and device

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