Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

Sztein, Alexander; Bowers, John E.; DenBaars, Steven P.; Nakamura, Shuji

doi:10.1063/1.4863420

Cited by 49 publications

(30 citation statements)

References 25 publications

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“…26 In agreement with the simulations, the high mobility is expected as a result of the much stronger electron confinement in the very short-period InN/InGaN SL structure with d b /d QW = 1. Essentially, as for this case the electron wave-function confined in the InN QW penetrates only very little into the adjacent InGaN barrier, the electrons are much less exposed to alloy scattering and charged dislocation scattering due to effective screening by the locally higher electron densities.…”

Section: B Thermoelectric Properties Of Inn/ingan Superlatticessupporting

confidence: 70%

“…Due to the semi-insulating nature, the influence of the substrate on the thermoelectric properties of the as-grown thin film heterostructures is negligible. 16,26,31 The (0001)-oriented, metal-polar films and SLs were grown on 10×10 mm 2 substrate pieces under slightly In-rich conditions, using a N-limited equivalent growth rate of Φ N = 6.4 nm/min. For the In-rich InGaN films a series of ∼1.1 µm-thick films were grown with different alloy compositions (nominal values of 0 < x(Ga) < 0.2), employing variable Ga-fluxes (equivalent growth rate of Φ Ga = 0.5 − 1.3 nm/min), a fixed In-flux of Φ In = 6.0 nm/min and growth temperature T TC of 530-550 • C as measured by a thermocouple (TC) attached to the backside of the substrate.…”

Section: Methodsmentioning

confidence: 99%

“…From the simulations we note that the squared electron wavefunction penetrates into the InGaN barriers for d b /d QW > 3, while much stronger confinement is achieved for d b /d QW <2, i.e., very short-period SLs. This is important from a thermoelectric perspective, since confined electrons in a high-mobility 2DEG at the InN/InGaN heterointerfaces may allow for enhanced electron mobility and electrical conductivity, 26 as further shown below. Figures 3(c)-3(e) present the structural and morphological properties of an exemplary as-grown short-period InN/InGaN SL according to the layer structure of Fig.…”

Section: B Thermoelectric Properties Of Inn/ingan Superlatticesmentioning

confidence: 99%

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Thermoelectric properties of In-rich InGaN and InN/InGaN superlattices

Sun

Haunschild

et al. 2016

AIP Advances

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The thermoelectric properties of n-type InGaN alloys with high In-content and InN/InGaN thin film superlattices (SL) grown by molecular beam epitaxy are investigated. Room-temperature measurements of the thermoelectric properties reveal that an increasing Ga-content in ternary InGaN alloys (0 < x(Ga) < 0.2) yields a more than 10-fold reduction in thermal conductivity (κ) without deteriorating electrical conductivity (σ), while the Seebeck coefficient (S) increases slightly due to a widening band gap compared to binary InN. Employing InN/InGaN SLs (x(Ga) = 0.1) with different periods, we demonstrate that confinement effects strongly enhance electron mobility with values as high as ∼820 cm2/V s at an electron density ne of ∼5×1019 cm−3, leading to an exceptionally high σ of ∼5400 (Ωcm)−1. Simultaneously, in very short-period SL structures S becomes decoupled from ne, κ is further reduced below the alloy limit (κ < 9 W/m-K), and the power factor increases to 2.5×10−4 W/m-K2 by more than a factor of 5 as compared to In-rich InGaN alloys. These findings demonstrate that quantum confinement in group-III nitride-based superlattices facilitates improvements of thermoelectric properties over bulk-like ternary nitride alloys.

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Section: B Thermoelectric Properties Of Inn/ingan Superlatticessupporting

confidence: 70%

Section: Methodsmentioning

confidence: 99%

Section: B Thermoelectric Properties Of Inn/ingan Superlatticesmentioning

confidence: 99%

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Thermoelectric properties of In-rich InGaN and InN/InGaN superlattices

Sun

Haunschild

et al. 2016

AIP Advances

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“…This is done by polarizing the electrical field of the GaN/AlN/Al 0.2 Ga 0.8 N superlattices, leading to a much higher electron mobility, increasing the ZT value to 0.08 at room temperature. 112 The future promise of III-Nitride for TE applications can be seen in Figure 5 which shows the variation of Seebeck coefficient for various binary materials and alloys.…”

Section: The Iii-nitrides For Thermoelectric Energy Harvestingmentioning

confidence: 99%

Review—The Current and Emerging Applications of the III-Nitrides

Zhou

Ghods

Saravade

et al. 2017

ECS J. Solid State Sci. Technol.

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III-Nitrides are attracting considerable attention as promising materials for a wide variety of applications due to their wide coverage of direct bandgap range, high electron mobility, high thermal stability and many other exceptional properties. The light-emitting diodes based on III-Nitrides revolutionize the solid-state lighting industry. III-Nitrides based solar cells and thermoelectric generators support the sustainable energy progress, and the III-Nitrides are better alternatives for power and radio frequency (RF) electronics compared with silicon. The doped III-Nitrides' magnetic properties and sensitivity to radiation can contribute to novel spintronic and nuclear detection devices. This paper will review III-nitride material properties and their corresponding applications in LEDs, solar cells, power and radio frequency (RF) electronics, magnetic devices, thermoelectrics and nuclear detection. The typical values of electrical, optical, thermoelectric, magnetic properties are cited, the current state of art investigations are reported, and the future applications are estimated. The III-Nitrides, typically composed of GaN and its alloys with Al and In, are compound semiconductor materials with superior properties and well developed growth techniques 1 that has enabled their use in a board range of applications. The III-Nitrides have a hexagonal wurtzite structure and a continuous alloy system with tunable direct bandgaps from 6.2 eV (AlN) through 3.4 eV (GaN) to 0.7 eV (InN) 2 ( Figure 1). This wide coverage of direct bandgap range from deepultraviolet (UV) to infrared region promises a variety of applications in optoelectronics, such as light-emitting diodes (LEDs), lasers, photodetectors and solar cells. GaN is recognized with high breakdown field, high thermal conductivity, and high electron mobility, making GaN an excellent candidate for high power and RF electronic devices. III-Nitrides exhibit high Seebeck coefficient and excellent temperature stability for high temperature thermoelectric applications. Doped GaN exhibit other unique properties with associated applications; such as transition and rare-earth metals doped GaN with magnetic properties, and indium (In)/gadolinium (Gd)/boron (B)/and lithium (Li) doped GaN for nuclear detection. The ability to access such a wide spectral region and these numerous applications has traditionally required the use of many different III-V materials and complex device structures before the advent of the III-Nitrides. [3][4][5][6][7][8][9] This paper will review various applications of III-Nitrides in including LEDs, solar cells, power and RF electronics, magnetic properties, thermoelectrics and nuclear detection applications, along with their development history, current state of art and future explorations. The III-Nitrides for Light-Emitting DiodesLight-Emitting Diodes are a type of solid state lighting (SSL) source with compact size, high energy efficiency and long lifetime. High brightness LEDs have various application in traffic lights, automobile brake ligh...

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“…3 GaN and related materials such as InN, AlN, and BN are also being investigated for applications in photocatalysis 4 and thermoelectrics. 5 In each of these applications, the presence of native defects (see Fig. 1) can strongly affect device performance.…”

Section: Introductionmentioning

confidence: 99%

Computationally predicted energies and properties of defects in GaN

2017

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Recent developments in theoretical techniques have significantly improved the predictive power of density-functional-based calculations. In this review, we discuss how such advancements have enabled improved understanding of native point defects in GaN. We review the methodologies for the calculation of point defects, and discuss how techniques for overcoming the band-gap problem of density functional theory affect native defect calculations. In particular, we examine to what extent calculations performed with semilocal functionals (such as the generalized gradient approximation), combined with correction schemes, can produce accurate results. The properties of vacancy, interstitial, and antisite defects in GaN are described, as well as their interaction with common impurities. We also connect the first-principles results to experimental observations, and discuss how native defects and their complexes impact the performance of nitride devices. Overall, we find that lower-cost functionals, such as the generalized gradient approximation, combined with band-edge correction schemes can produce results that are qualitatively correct. However, important physics may be missed in some important cases, particularly for optical transitions and when carrier localization occurs.

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Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

Cited by 49 publications

References 25 publications

Thermoelectric properties of In-rich InGaN and InN/InGaN superlattices

Thermoelectric properties of In-rich InGaN and InN/InGaN superlattices

Review—The Current and Emerging Applications of the III-Nitrides

Computationally predicted energies and properties of defects in GaN

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