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![a The band gap energy Eg(Γ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_\mathrm{g}(\Gamma )$$\end{document} as a function of temperature. In the figure, blue stars illustrate our calculated data; the solid red circles and green squares represent the photoluminescence excitation and luminescence measurements of Nakayama et al. [21] and Cingolani et al. [24] for comparison, respectively. b The calculated energy gap and cut-off wavelength λc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda _\mathrm{c}$$\end{document}, as a function of the well GaAs thickness (Color figure online)](publication/289586242/figure/fig3/AS:961805887213585@1606323801671/a-The-band-gap-energy-EgGdocumentclass12ptminimal-usepackageamsmath.gif)
a The band gap energy Eg(Γ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_\mathrm{g}(\Gamma )$$\end{document} as a function of temperature. In the figure, blue stars illustrate our calculated data; the solid red circles and green squares represent the photoluminescence excitation and luminescence measurements of Nakayama et al. [21] and Cingolani et al. [24] for comparison, respectively. b The calculated energy gap and cut-off wavelength λc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda _\mathrm{c}$$\end{document}, as a function of the well GaAs thickness (Color figure online)
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![a The band gap energy Eg(Γ)\documentclass[12pt]{minimal}...](publication/289586242/figure/fig3/AS:961805887213585@1606323801671/a-The-band-gap-energy-EgGdocumentclass12ptminimal-usepackageamsmath_Q320.jpg)
We report here the electronic band structures of symmetric type I GaAs ((Formula presented.) nm)/AlAs ((Formula presented.) nm) superlattice as a function of the well thickness (Formula presented.) and the effect of the valence band offset (Formula presented.), the ratio (Formula presented.)/(Formula presented.), and the temperature on the band gap...
Citations
... Semiconductor superlattices (SLs), each consisting of alternating thin layers of two or more different semiconductors, exhibit unique properties and are widely used in novel optical and electronic devices. [1][2][3][4] Especially, the GaAs/AlAs SL has received wide attention in the applications of high electron mobility transistor (HEMT) and quantum cascade laser (QCL). [5][6][7][8] However, when the SL materials are used in irradiation environments such as aerospace field, [9] high energy physics field, [10] and nuclear physics field, [11] point defects may appear in GaAs/AlAs SL, resulting in the failure of the SL-based devices. ...
When the GaAs/AlGaAs superlattice-based devices are used under irradiation environments, point defects may be created and ultimately deteriorate their electronic and transport properties. Thus, understanding the properties of point defects like vacancies and interstitials is essential for the successful application of semiconductor materials. In the present study, first-principles calculations are carried out to explore the stability of point defects in GaAs/Al 0.5 Ga 0.5 As superlattice and their effects on electronic properties. The results show that the interstitial defects and Frenkel pair defects are relatively difficult to form, while the antisite defects are favorably created generally. Besides, the existence of point defects generally modifies the electronic structure of GaAs/Al 0.5 Ga 0.5 As superlattice significantly, and most of the defective SL structures possess metallic characteristics. Considering the stability of point defects and carrier mobility of defective states, we propose an effective strategy that Al As , Ga As , and Al Ga antisite defects are introduced to improve the hole or electron mobility of GaAs/Al 0.5 Ga 0.5 As superlattice. The obtained results will contribute to the understanding of the radiation damage effects of the GaAs/AlGaAs superlattice, and provide a guidance for designing highly stable and durable semiconductor superlattice-based electronics and optoelectronics for extreme environment applications.
... effect, 3,4 quantum confinement of elementary particles, 5,6 development of quantum well lasers, 7,8 quantum cascade lasers, 9,10 etc., with large-scale societal impacts. 11 While most of these heterostructures are composed of lattice-matched semiconductors such as GaAs/AlAs with their electronic band-offset providing essential functionalities, 12,13 metal/semiconductor superlattice (SL) heterostructures have not gained much attention until very recently. 14 Epitaxial single-crystalline metal/semiconductor superlattices with tunable Schottky barrier heights could lead to highly efficient thermionic emission-based thermoelectric energy converters, [15][16][17] hot-electron devices for solar-energy conversion, 18,19 terahertz optoelectronics, exotic optical metamaterials with hyperbolic dispersions and large densities of photonic states, etc. [20][21][22][23] However, the material's compatibility and growth challenges had primarily limited the progress in the development of such "man-made" crystals for a long time. ...
... 36,40 The full-width-at-the-half-maxima (FWHM) of the rocking curve corresponding to the 002 peak was found to be 0.045°(not shown here) that indicates its nominal single-crystalline nature. Since the Al 0.72 Sc 0.28 N thin film with 72% AlN mole-fractions is metastable in the rocksalt crystal structure, 13 prior to the Al 0.72 Sc 0.28 N deposition, a 20 nm TiN seed layer was deposited on MgO substrates. HRXRD analysis revealed that the TiN/Al 0.72 Sc 0.28 N film grows with the 002 orientations on the MgO substrate with a lattice-constant of 4.27 Å. ...
Epitaxial lattice-matched TiN/(Al,Sc)N metal/semiconductor superlattices have attracted significant interest in recent years for their potential applications in thermionic emission-based thermoelectric devices, optical hyperbolic metamaterials, and hot-electron-based solar-energy converters, as well as for the fundamental studies on the electron, photon, and phonon propagation in heterostructure materials. In order to achieve high efficiency devices and for the quest to discover new physics and device functionalities, it is extremely important that the superlattices exhibit atomically sharp and abrupt interfaces with minimal interface mixing and surface roughness. Moreover, as the energy transport across the cross-plane direction of these superlattices depends on the interface-properties, it is important to characterize the interfacial electronic structure and the chemistry of bond formation. Employing a combination of soft x-ray scattering techniques such as x-ray diffraction and synchrotron-based x-ray reflectivity, in this article, we demonstrate sharp and abrupt TiN/(Al,Sc)N superlattice interfaces with an asymmetric interface roughness ranging from two-to-three unit cells. Synchrotron-based soft x-ray absorption analysis revealed similar peak positions, line shapes, and absorption edges of different atoms in the individual thin films and in the superlattices, which demonstrate that the oxidation state of the atoms remains unchanged and rules-out the secondary structure or phase formation at the interfaces. The x-ray scattering results were further verified by aberration-corrected high-resolution scanning transmission electron microscopy imaging and energy dispersive x-ray spectroscopy mapping analysis. These results will be important for understanding of the transport properties of metal/semiconductor superlattices and for designing superlattice-based energy conversion devices.
... It is noted that gallium arsenide (GaAs) and aluminum arsenide (AlAs) are perfectly lattice matched, and few difficulties are expected in the growth of (GaAs) m /(AlAs) n semiconductor superlattice (SL), which consists of m monolayers of GaAs alternating with n monolayers of AlAs. The artificial SL has been widely used in different applications like the optoelectronic devices with quantum cascade laser, high-frequency oscillators and thermoelectric devices [2][3][4][5][6][7][8][9] , due to the new physical phenomena such as quantum confinement, Brillouin-zone folding and the obtaining of a direct-gap superlattice from their indirect-gap constitutes 10 . In the application field of military and aerospace, the semiconductor materials are exposed to different radiation environments, which may result in defect generation, migration and aggregation, and ultimately may deteriorate their optical and electronic properties and influence their performance which may lead to permanent failure [10][11][12][13][14][15] . ...
... molecular beam epitaxy and metal-organic vapour phase epitaxy) 1 . The semiconductor (GaAs) m /(AlAs) n superlattices (SLs), in which m and n denote the number of stacking periodicity, have been widely applied in various optoelectronic devices, due to their unusual physical properties related to luminescence and optical absorption, etc [2][3][4][5][6][7] . Despite extensive studies on the electronic and optical properties of GaAs/AlAs SLs, such as band gap and absorption coefficient, there still lacks a comprehensive understanding of the effect of stacking periodicity on the optoelectronic properties of GaAs/AlAs SLs for its application as near infrared detector. ...
The effects of stacking periodicity on the electronic and optical properties of GaAs/AlAs superlattice have been explored by density functional theory calculations. Among the (GaAs)m/(AlAs)m, (GaAs)1/(AlAs)m and (GaAs)m/(AlAs)1 (m = 1 to 5) superlattices, the band gaps of (GaAs)m/(AlAs)1 superlattices decrease significantly as the layer of GaAs increases, and the cut-off wavelengths are found to locate in the near infrared region. For (GaAs)m/(AlAs)1 SLs, the conduction bands shift toward Fermi level, resulting in the smaller band gap, while conduction bands of (GaAs)1/(AlAs)n SLs slightly shift to higher energy, which lead to comparable band gaps. The layer number of GaAs shows negligible effects on the reflectivity spectra of superlattice structures, while the absorption coefficient shows a red-shift with the increasing layer of GaAs, which is beneficial for the application of GaAs/AlAs superlattice in the field of near infrared detector. These results demonstrate that controlling the number of GaAs layers is a good method to engineer the optoelectronic properties of GaAs/AlAs superlattice.
... The dispersion relation for electrons, light and heavy holes bands is written as [9,10]: cos 2 2 1 1 2 1 2 p 2 2 1 1 2 ...
... The dispersion relation for electrons, light and heavy holes bands is written as [9,10]: ...
We report here the effect of layers thickness and
temperature on electronic transport of nanostructure by
calculation of band structure of two superlattices SL1
InAs(d1)/Gasb(d2) of type II and SL2 HgTe/CdTe of type III for
infrared detection application. These studies were done using
the envelope function formalism. We calculated the energy of
carriers as a function of layers thickness, the ration d1/d2 and
the temperature. The calculated density of states and Fermi
level energy shows that temperature generated transitions from
quasi bidimensional (Q2D) to three dimensional (3D) in the two
SL. The later occurred near 20 K in the p type SL1 and near 84
K in SL2 with p type to n type conductivity transition. We found
that these SL are mid infrared and terahertz detectors. The
electronic transport parameters calculated here are necessary
for the design of infrared photo-detectors.
... The superlattice (SL) is an artificial material consisting of alternating thin layers of two or more different components. The (GaAs) n /(AlAs) m is one of the most important SL since the development of high electron mobility transistors (HEMT) and quantum cascade lasers (QCLs) a few decades ago [1][2][3][4][5][6]. Recently with the advances of film epitaxy and nanofabrication techniques, the (GaAs) n /(AlAs) m based SLs and nanodevices with (n + m) ranging from 2 to 10 have demonstrated exciting physical properties related to luminescence and optical absorption, two-phonon absorption, and Raman as well as infrared spectra, which thus found promising applications in optoelectronics, sensing, LED, energy and laser related civilian and industrial areas [7][8][9][10][11][12]. ...
Advanced semiconductor superlattices play important roles in critical future high-tech applications such as aerospace, high-energy physics, gravitational wave detection, astronomy, and nuclear related areas. Under such extreme conditions like high irradiative environments, these semiconductor superlattices tend to generate various defects that ultimately may result in the failure of the devices. However, in the superlattice like GaAs/AlAs, the phase stability and impact on the device performance of point defects are still not clear up to date. The present calculations show that in GaAs/AlAs superlattice, the antisite defects are energetically more favorable than vacancy and interstitial defects. The AsX (X = Al or Ga) and XAs defects always induce metallicity of GaAs/AlAs superlattice, and GaAl and AlGa antisite defects have slight effects on the electronic structure. For GaAs/AlAs superlattice with the interstitial or vacancy defects, significant reduction of band gap or induced metallicity is found. Further calculations show that the interstitial and vacancy defects reduce the electron mobility significantly, while the antisite defects have relatively smaller influences. The results advance the understanding of the radiation damage effects of the GaAs/AlAs superlattice, which thus provide guidance for designing highly stable and durable semiconductor superlattice based electronic and optoelectronics for extreme environment applications.
... Recently, Jiang et al. found Ga and Al atoms in GaAs/AlAs SLs are more susceptible to the radiation than those in the bulk AlAs and GaAs, in which the created defects have a profound effect on the electronic properties of GaAs/AlAs SLs (even metallicity are induced in some cases) [14]. Barkissy et al. reported the band gap of GaAs/AlAs SLs performed in the envelope function formalism with respect of thickness ratio [15]. ...
... In the case of (GaAs) m (AlAs) n SLs, the value of E g (m = n) gradually decayed according to the exponential law E g (m = n) = E g 0 + Ae −km . In the latter case, the values of E g (m = n) were in food agreement with the experimental measurements in published articles [12,[15][16][17][18]26,27]: E g (m = n = 1) = 2.120 eV; E g (m = n = 2) = 2.097 eV, E g (m = n = 3) = 2.099 eV, E g (m = n = 4) = 2.067 eV, E g (m = n = 5) = 2.015 eV, E g (m = n = 7) = 1.918 eV, E g (m = n = 8) = 1.881 eV, and E g (m = n = 10) = 1.766 eV. For example, Fujimoto et al. found the band gaps of (GaAs) n (AlAs) n SLs with n = 1-15 varied according to the exponential decay with increasing period number [12], which is consistent with the experimental measurements by Jiang et al. [27] and our finding in the present work. ...
... Å)/AlAs (d = 28.3 Å) SL as 1.748 eV [15], which is close to our calculated result (the band gap of (GaAs) 5 (AlAs) 5 SL was 1.684 eV); Fujimoto et al. also measured the band gap energy of (GaAs) 5 (AlAs) 5 SL as 1.910 eV through photoluminescence measurements at room temperature [12]. The difference between experimental measurements and theoretical calculations is ascribed to the measurement error, temperature effects, theoretical approximation, and so on. ...
As important functional materials, the electronic structure and physical properties of (GaAs)m(AlAs)n superlattices (SLs) have been extensively studied. However, due to limitations of computational methods and computational resources, it is sometimes difficult to thoroughly understand how and why the modification of their structural parameters affects their electronic structure and physical properties. In this article, a high-throughput study based on density functional theory calculations has been carried out to obtain detailed information and to further provide the underlying intrinsic mechanisms. The band gap variations of (GaAs)m(AlAs)n superlattices have been systematically investigated and summarized. They are very consistent with the available reported experimental measurements. Furthermore, the direct-to-indirect-gap transition of (GaAs)m(AlAs)n superlattices has been predicted and explained. For certain thicknesses of the GaAs well (m), the band gap value of (GaAs)m(AlAs)n SLs exponentially increases (increasing n), while for certain thicknesses of the AlAs barrier (n), the band gap value of (GaAs)m(AlAs)n SLs exponentially decreases (increasing m). In both cases, the band gap values converge to certain values. Furthermore, owing to the energy eigenvalues at different k-points showing different variation trends, (GaAs)m(AlAs)n SLs transform from a Γ-Γ direct band gap to Γ-M indirect band gap when the AlAs barrier is thick enough. The intrinsic reason for these variations is that the contributions and positions of the electronic states of the GaAs well and the AlAs barrier change under altered thickness conditions. Moreover, we have found that the binding energy can be used as a detector to estimate the band gap value in the design of (GaAs)m(AlAs)n devices. Our findings are useful for the design of novel (GaAs)m(AlAs)n superlattices-based optoelectronic devices.
... The general expression of the dispersion relation for light particles (electrons and light holes) and heavy holes subbands is given by [9,10] The investigated sample is HgTe/CdTe with d 1 (HgTe)= 45 Å and d 2 (CdTe)= 48 Å. Consequently, d 2 /d 1 =1.07 and the superlattice period is d= d 1 +d 2 = 93 Å. ...
... It is noted that gallium arsenide (GaAs) and aluminum arsenide (AlAs) are perfectly lattice matched, and few difficulties are expected in the growth of (GaAs) m /(AlAs) n semiconductor superlattice (SL), which consists of m monolayers of GaAs alternating with n monolayers of AlAs. The artificial SL has been widely used in different applications like the optoelectronic devices with quantum cascade laser, high-frequency oscillators and thermoelectric devices [2][3][4][5][6][7][8][9] , due to the new physical phenomena such as quantum confinement, Brillouin-zone folding and the obtaining of a direct-gap superlattice from their indirect-gap constitutes 10 . In the application field of military and aerospace, the semiconductor materials are exposed to different radiation environments, which may result in defect generation, migration and aggregation, and ultimately may deteriorate their optical and electronic properties and influence their performance which may lead to permanent failure [10][11][12][13][14][15] . ...
In this study, the low energy radiation responses of AlAs, GaAs and GaAs/AlAs superlattice are simulated and the radiation damage effects on their electronic structures are investigated. It is found that the threshold displacement energies for AlAs are generally larger than those for GaAs, i.e., the atoms in AlAs are more difficult to be displaced than those in GaAs under radiation environment. As for GaAs/AlAs superlattice, the Ga and Al atoms are more susceptible to the radiation than those in the bulk AlAs and GaAs, whereas the As atoms need comparable or much larger energies to be displaced than those in the bulk states. The created defects are generally Frenkel pairs, and a few antisite defects are also created in the superlattice structure. The created defects are found to have profound effects on the electronic properties of GaAs/AlAs superlattice, in which charge transfer, redistribution and even accumulation take place, and band gap narrowing and even metallicity are induced in some cases. This study shows that it is necessary to enhance the radiation tolerance of GaAs/AlAs superlattice to improve their performance under irradiation.
