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RISS 인기검색어
- 검색키워드
- 저자 : Bakhtiar Ul Haq (검색결과 4 건)
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Ul Haq, Bakhtiar,Ahmed, R.,Rhee, Joo Yull,Shaari, A.,AlFaify, S.,Ahmed, M. Elsevier 2017 Journal of alloys and compounds Vol.693 No.-
<P><B>Abstract</B></P> <P>Capable of achieving wide control over energy band gap and following optoelectronic properties; the highly mismatched alloys (HMAs) are considered to be promising materials for solar energy conversion devices. The dramatic restructuring of energy bands and density of states in HMAs caused by the replacement of anions with distinctly-mismatched isovalent constituents could further be an important course in improving their thermoelectric efficiency. In this paper, we attempt to explore and address the composition-induced modifications in the electronic band structure and the resultant effects on optical spectra and thermoelectric coefficients of GaN<SUB>1−x</SUB>Sb<SUB>x</SUB> based HMAs in the framework of density functional theory. We observe, the substitution of N by Sb, considerably affects its band structure and split the conduction band minimum (CBM) into sub-bands. With increasing Sb composition, the lowest sub-band stemmed from N-s electrons has experienced drastic downward shift leading to energy gap narrowing. Interestingly, the energy gap narrowing along R- Γ is found to be faster than that of Γ- Γ point leading to an amazing direct to indirect band gap crossover. On the other hand, the composition-induced energy gap narrowing stimulates the red-shift in fundamental absorption edge in both ultraviolet and the infrared regime, making the GaNSb potentially useful material for photovoltaic applications. In addition, substantial effect on the thermoelectric coefficients of GaNSb is also observed via Sb substitution. We obtain larger Seebeck coefficient, improved power factors and figure of merit (ZT) for GaNSb at low Sb substitution and found diminishing effect with the further increase of Sb composition. With enhanced Seebeck coefficient, power factor and ZT values at modest doping levels, GaNSb alloy could be a promising candidate for near or above room temperature thermoelectric applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Alloying of GaNSb across entire composition in the framework of DFT. </LI> <LI> The striking direct to indirect energy gap cross over. </LI> <LI> Enhanced absorption in ultraviolet, visible and infrared energy regime. </LI> <LI> Comprehensive investigations of thermoelectric properties of GaNSb alloy. </LI> </UL> </P>
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Bakhtiar Ul Haq,R. Ahmed,Mazmira Mohamad,A. Shaari,이주열,S. AlFaify,Mohammed Benali Kanoun,Souraya Goumri-Said 한국물리학회 2017 Current Applied Physics Vol.17 No.2
Highly mismatched alloys (HMAs) are getting a substantial interest of researchers because of holding competence of rapid change in physical properties with minor compositional change and consequently showing their potential for solar energy and photovoltaic applications. In the present density functional theory based work, we design HMAs from the extremely dissimilar GaP (semiconductor) and GaBi (semimetal). The alloying of the two compounds with unmatched electronic characteristics has triggered a rapid reduction in the energy gap of GaPBi. The energy gap is reduced by 39.3 meV for every 1% increase in Bi composition. The semiconductor behavior of GaPBi based HMAs is found to be transformed to semimetallic for replacing 64.6% of P atoms by Bi. Unlike the conventional alloys, the variation in the electronic energy gap of GaP1-xBix shows deviation from the Vegard's formalism. Where the optical properties are strongly influenced with the narrowing energy gap of GaPBi. For the Bi-rich GaPBi, the notable red shift is observed in optical dielectric function and absorption spectra. Moreover, the larger atomic size of Bi has enhanced the lattice parameters of Bi-rich GaPBi. The GaPBi based HMAs with tunable energy gap in the span of 2.51 eVe0 eV and the interesting optical properties highlight them prospective materials for optoelectronic applications.
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Haq, Bakhtiar Ul,Ahmed, R.,Mohamad, Mazmira,Shaari, A.,Rhee, JooYull,AlFaify, S.,Kanoun, Mohammed Benali,Goumri-Said, Souraya ELSEVIER 2017 Current Applied Physics Vol.17 No.2
<P>Highly mismatched alloys (HMAs) are getting a substantial interest of researchers because of holding competence of rapid change in physical properties with minor compositional change and consequently showing their potential for solar energy and photovoltaic applications. In the present density functional theory based work, we design HMAs from the extremely dissimilar GaP (semiconductor) and GaBi (semi metal). The alloying of the two compounds with unmatched electronic characteristics has triggered a rapid reduction in the energy gap of GaPBi. The energy gap is reduced by 39.3 meV for every 1% increase in Bi composition. The semiconductor behavior of GaPBi based HMAs is found to be transformed to semi metallic for replacing 64.6% of P atoms by Bi. Unlike the conventional alloys, the variation in the electronic energy gap of GaP1-xBix shows deviation from the Vegard's formalism. Where the optical properties are strongly influenced with the narrowing energy gap of GaPBi. For the Bi-rich GaPBi, the notable red shift is observed in optical dielectric function and absorption spectra. Moreover, the larger atomic size of Bi has enhanced the lattice parameters of Bi-rich GaPBi. The GaPBi based HMAs with tunable energy gap in the span of 2.51 eV-0 eV and the interesting optical properties highlight them prospective materials for optoelectronic applications. (C) 2016 Elsevier B.V. All rights reserved.</P>
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Ul Haq Bakhtiar,Kim Se-Hun,Alsardia M.M.,Khadka I.B.,Chaudhry Aijaz Rasool,AlFaify S.,Ahmed R.,Shah Zulfiqar Ali 한국물리학회 2023 Current Applied Physics Vol.49 No.-
In recent years, exploring new polytypes of III-V semiconductors has been widely practiced for the development of thermoelectric devices of high efficiency. In this work, the thermoelectric properties of new polytypes, namely the wurtzite(wz), Berrylium oxide (β-BeO), Nickel arsenide (NiAs), Silicon carbide (SiC), and Titanium arsenide (TiAs) phases of GaN have been investigated using the first-principles approaches. It is found that the p-type of doping induces enhancement of the power factors (PFs) and figure-of-merits (zT) of the GaN polytypes. The optimal p-type doping for PFs has been recognized as - 1.67 eV for wz-GaN, - 1.78 eV for β-BeO-GaN, - 1.33 eV for NiAs-GaN, - 1.58 eV for SiC-GaN, and - 1.48 eV for TiAs-GaN. These optimal p-type doping has induced the room-temperature PFs as high as 13.75 × 1010 W/mK2s recorded for wz-GaN, 13.61 × 1010 W/mK2s for β-BeO-GaN, 41.14 × 1010 W/mK2s for NiAs-GaN, 14.06 × 1010 W/mK2s for SiC-GaN, and 49.21 × 1010 W/mK2s for TiAs-GaN. Furthermore, the PFs of the GaN polytypes are enhanced by increasing the temperature. Due to such significant PFs, the zT values corresponding to p-type doping have been recorded as 1.013 for wz-GaN, 0.998 for β-BeO-GaN, 1.00 for NiAs-GaN, 1.015 for SiC-GaN, and 0.999 for TiAs-GaN. Moreover, we comprehensively discussed the electrical and thermal conductivities and Seebeck coefficients (S) for the predicted GaN polytypes. The results of the thermoelectric properties presented in this study reveal the predicted GaN polytypes may find interesting applications in thermoelectric devices for clean energy harvesting.
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