Investigation of valence-band splitting in InN by low-temperature photoreflectance spectroscopy

Lin, Kwang‐Lung; Chen, Yen Jen; Cheng, Yung Chen; Gwo, Shangjr

doi:10.7567/jjap.54.031001

Cited by 5 publications

(3 citation statements)

References 35 publications

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“…This ordering of the valence bands corresponds to the positive SOC, determined by the positive values of two SOC parameters and , which are referred to as the SOC constants along the c axis of the wurtzite lattice and in the plane perpendicular to the c axis, respectively. The reported values of and in InN and GaN, obtained from ab-initio band structure calculations and experiments, were in the range from 1 to 25 meV 21 – 23 . The positive SOC in GaN and InN was taken into account so far in the study of the TPT in InN/GaN and InGaN/GaN QWs 13 – 15 .…”

Section: Introductionmentioning

confidence: 99%

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Łepkowski

Bardyszewski

2018

Sci Rep

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We study the influence of negative spin-orbit coupling on the topological phase transition and properties of the topological insulator state in InGaN-based quantum wells grown along c axis of the wurtzite lattice. The realistic eight-band k·p method with relativistic and nonrelativistic linear-k terms is employed. Our calculations show that the negative spin-orbit coupling in InN is not an obstacle to obtain the topological insulator phase in InN/InGaN and InGaN/GaN quantum wells. The bulk energy gap in the topological insulator state can reach 2 meV, which allows experimental verification of the edge state transport in these materials. The topological phase transition occurs due to the band inversion between the highest light hole subband and the lowest conduction subband, and almost always is mediated by the two-dimensional Weyl semimetal, arising from an anticrossing of these subbands at zero in-plane wave vector. However, for certain InGaN/GaN quantum wells, we find that the magnitude of this anticrossing vanishes, leading to the appearance of the Dirac semimetal. The novel transition between the Weyl and Dirac semimetals originates from vanishing of the average in-plane spin-orbit interaction parameter, which decouples the conduction subband from the light hole subband at zero in-plane wave vector.

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Section: Introductionmentioning

confidence: 99%

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Łepkowski

Bardyszewski

2018

Sci Rep

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“…Кроме электронных InAs и InSb из полупроводниковых соединений A 3 B 5 такая же ситуация с приповерхностным изгибом зон и возникновением на поверхности обогащенного электронами слоя наблюдается в InN, ФО которого измерялось в [122,123]. Замечено, что для данного материала приповерхностное электрическое поле In-полярной поверхности InN меньше, чем Nполярной [124].…”

Section: арсенид индия (Inas)unclassified

Инфракрасное Фотоотражение Полупроводниковых Материалов a-=sup=-3-=/Sup=-B-=sup=-5-=/Sup=- ( О Б З О Р )

Комков¹

2021

Физика Твердого Тела

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Photoreflectance is a contactless type of modulation optical spectroscopy. It is used to study the band structure features of monocrystalline semiconductors, their doping level, the composition of alloys, as well as surface and interface band bending. Using high-quality GaAs as an example, the possibilities of describing the photoreflectance lineshape by one-electron and exciton models are demonstrated. The spectra of ultrapure samples of this material exhibit an oscillating structure well described by excitonic effects. For III-V alloys, a review of photoreflectance results concerning the effect of composition and temperature on the band gap and spin-orbit splitting is carried out. Determination of the position of the Fermi level on the surface (Fermi level pinning) for III-V crystals is considered. The currently developing technique for measuring photoreflectance in the mid-infrared range (photomodulation Fourier transform infrared spectroscopy) is described in detail. It is shown that phase correction plays a decisive role in such measurements. Original results demonstrate the capabilities of this method in a wide wavelength range.

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“…This phenomenon, called the polarization-induced TPT, was initially proposed for InN/GaN QWs with L TI qw equal to four atomic monolayers (MLs) [24]. The predicted values of E TI 2Dg in these structures depend significantly on the assumed intrinsic SOI in InN, which is still under scientific debate [26][27][28][29]. It was found that E TI 2Dg can reach 5 meV when a positive SOI of the order of a few meV is assumed in InN, or it can be about 1.25 meV when a negative SOI in InN is considered [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Quantum Spin Hall Effect in Two-Monolayer-Thick InN/InGaN Coupled Multiple Quantum Wells

Łepkowski

2023

Nanomaterials

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In this study, we present a theoretical study of the quantum spin Hall effect in InN/InGaN coupled multiple quantum wells with the individual well widths equal to two atomic monolayers. We consider triple and quadruple quantum wells in which the In content in the interwell barriers is greater than or equal to the In content in the external barriers. To calculate the electronic subbands in these nanostructures, we use the eight-band k∙p Hamiltonian, assuming that the effective spin–orbit interaction in InN is negative, which represents the worst-case scenario for achieving a two-dimensional topological insulator. For triple quantum wells, we find that when the In contents of the external and interwell barriers are the same and the widths of the internal barriers are equal to two monolayers, a topological insulator with a bulk energy gap of 0.25 meV can appear. Increasing the In content in the interwell barriers leads to a significant increase in the bulk energy gap of the topological insulator, reaching about 0.8 meV. In these structures, the topological insulator can be achieved when the In content in the external barriers is about 0.64, causing relatively low strain in quantum wells and making the epitaxial growth of these structures within the range of current technology. Using the effective 2D Hamiltonian, we study the edge states in strip structures containing topological triple quantum wells. We demonstrate that the opening of the gap in the spectrum of the edge states caused by decreasing the width of the strip has an oscillatory character regardless of whether the pseudospin-mixing elements of the effective Hamiltonian are omitted or taken into account. The strength of the finite size effect in these structures is several times smaller than that in HgTe/HgCdTe and InAs/GaSb/AlSb topological insulators. Therefore, its influence on the quantum spin Hall effect is negligible in strips with a width larger than 150 nm, unless the temperature at which electron transport is measured is less than 1 mK. In the case of quadruple quantum wells, we find the topological insulator phase only when the In content in the interwell barriers is larger than in the external barriers. We show that in these structures, a topological insulator with a bulk energy gap of 0.038 meV can be achieved when the In content in the external barriers is about 0.75. Since this value of the bulk energy gap is very small, quadruple quantum wells are less useful for realizing a measurable quantum spin Hall system, but they are still attractive for achieving a topological phase transition and a nonlocal topological semimetal phase.

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Investigation of valence-band splitting in InN by low-temperature photoreflectance spectroscopy

Cited by 5 publications

References 35 publications

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Инфракрасное Фотоотражение Полупроводниковых Материалов a-=sup=-3-=/Sup=-B-=sup=-5-=/Sup=- ( О Б З О Р )

Quantum Spin Hall Effect in Two-Monolayer-Thick InN/InGaN Coupled Multiple Quantum Wells

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