Composition-dependent band gaps and indirect–direct band gap transitions of group-IV semiconductor alloys

2015 ◽  
Vol 17 (33) ◽  
pp. 21605-21610 ◽  
Author(s):  
Zhen Zhu ◽  
Jiamin Xiao ◽  
Haibin Sun ◽  
Yue Hu ◽  
Ronggen Cao ◽  
...  
Keyword(s):  
Band Gap ◽  
Transition Point ◽  
Reliable Method ◽  
Group Iv ◽  
Band Gaps ◽  
Semiconductor Alloys ◽  
Direct Band Gap ◽  
Group Iv Semiconductor ◽  
Direct Band

Obtaining the value of the band gap and the composition of an indirect–direct band gap transition point for group-IV semiconductor alloys by an efficient and reliable method.

Sn-based Group-IV Semiconductors on Si: New Infrared Materials and New Templates for Mismatched Epitaxy

2005 ◽  
Vol 891 ◽  
Author(s):  
John Tolle ◽  
Radek Roucka ◽  
Vijay D'Costa ◽  
Jose Menendez ◽  
Andrew Chizmeshya ◽  
...  
Keyword(s):  
Band Gap ◽  
Buffer Layer ◽  
Lattice Mismatch ◽  
Group Iv ◽  
Buffer Layers ◽  
Direct Band Gap ◽  
Group Iv Semiconductors ◽  
Direct Band ◽  
Infrared Materials ◽  
Edge Dislocations

ABSTRACTWe report growth and properties of GeSn and SiGeSn alloys on Si (100). These materials are prepared using a novel CVD approach based on reactions of Si-Ge hydrides and SnD4. High quality GeSn films with Sn contents up to 20%, and strain free microstructures have been obtained. The lattice mismatch between the films and Si is relieved by Lomer edge dislocations located at the interface. This material is of interest due to the predicted cross-over to a direct gap semiconductor for moderate Sn concentrations. We find that the direct band gap, and, consequently, the main absorption edge, shifts monotonically to lower energies as the Sn concentration is increased. The compositional dependence of the direct band gap shows a strong bowing, such that the direct band gap is reduced to 0.4 eV (from 0.8 eV for pure Ge) for a concentration of 14% Sn. The ternary SiGeSn alloy has been grown for the first time on GeSn buffer layers. This material opens up entirely new opportunities for strain and band gap engineering using group-IV materials via decoupling of strain and composition. Our SiGeSn layers have lattice constants above and below that of pure Ge, and depending on the thickness and composition of the underlying buffer layer they can be grown relaxed, with compressive, or with tensile strain. In addition to acting as a buffer layer for the growth of SiGeSn, we have found that GeSn can act as a template for the subsequent growth of a variety of materials, including III-V semiconductors.

Green Synthesis of Ge1-xSnx Alloy Nanoparticles for Optoelectronic Applications

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1216
Author(s):  
Gopal Singh Attar ◽  
Mimi Liu ◽  
Cheng-Yu Lai ◽  
Daniela R. Radu
Keyword(s):  
Band Gap ◽  
Complementary Metal Oxide Semiconductor ◽  
Cmos Technology ◽  
Oxide Semiconductor ◽  
Colloidal Synthesis ◽  
Alloy Nanoparticles ◽  
Direct Band Gap ◽  
Si Photonics ◽  
Group Iv Semiconductor ◽  
Direct Band

Compositionally controlled, light-emitting, group IV semiconductor nanomaterials have potential to enable on-chip data communications and infrared (IR) imaging devices compatible with the complementary metal−oxide−semiconductor (CMOS) technology. The recent demonstration of a direct band gap laser in Ge-Sn alloys opens avenues to the expansion of Si-photonics. Ge-Sn alloys showed improved effective carrier mobility as well as direct band gap behavior at Sn composition above 6–11%. In this work, Ge1−xSnx alloy nanoparticles with varying Sn compositions from x = 0.124 to 0.178 were prepared via colloidal synthesis using sodium borohydride (NaBH4), a mild and non-hazardous reducing reagent. Successful removal of the synthesized long-alkyl-chain ligands present on nanoparticles’ surfaces, along with the passivation of the Ge-Sn nanoparticle surface, was achieved using aqueous (NH4)2S. The highly reactive surface of the nanoparticles prior to ligand exchange often leads to the formation of germanium oxide (GeO2). This work demonstrates that the (NH4)2S further acts as an etching reagent to remove the oxide layer from the particles’ surfaces. The compositional control and long-term stability will enable the future use of these easily prepared Ge1−xSnx nanoalloys in optoelectronic devices.

scholarly journals Towards a direct band gap group IV Ge-based material

2019 ◽  
Vol 92 ◽  
pp. 39-46 ◽  
Author(s):  
Tuan T. Tran ◽  
Jay Mathews ◽  
J.S. Williams
Keyword(s):  
Band Gap ◽  
Group Iv ◽  
Direct Band Gap ◽  
Direct Band

scholarly journals The Effect of Band-Gap on TiO2 Thin Film Considering Various Parameters

2021 ◽  
Vol 19 ◽  
pp. 45-52
Author(s):  
Majedul Haque Mithun ◽  
Abu Sayed ◽  
Imteaz Rahaman
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Tio2 Thin Film ◽  
Sol Gel ◽  
Band Gaps ◽  
Tio2 Thin Films ◽  
Direct Band Gap ◽  
Direct Band ◽  
Indirect Band Gap ◽  
Absorbance Spectra

The aim of this work is to measure the effect of band-gap on TiO2 thin films by changing tetrabutylorthotitanate (TBOT), diethanolamine (DEA), and temperature. The sol-gel method is experimentally introduced to find out the better band-gap of TiO2 thin films by varying the concentration of TBOT (4 ml to 10 ml), DEA (2 ml to 5 ml), and temperature (350°C to 650°C). With the help of an ultraviolet-visible spectrophotometer for the wavelength of 300-900 nm, these thin films are characterized concerning optical properties (transmittance spectra, absorbance spectra, direct band-gap, and indirect band-gap). The direct and indirect band-gaps are found 3.38 eV and 3.25 eV respectively, which are close to or within the standard band-gap range of TiO2 (3.2 eV to 3.35 eV) and are found at 8 ml TBOT, 3 ml DEA, and a temperature of 550°C.

scholarly journals Low-temperature photoluminescence of CuSe2 nano-objects in selenium thin films

2017 ◽  
Vol 11 (2) ◽  
pp. 127-135 ◽  
Author(s):  
Martina Gilic ◽  
Milica Petrovic ◽  
Jovana Cirkovic ◽  
Novica Paunovic ◽  
Svetlana Savic-Sevic ◽  
...  
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Room Temperature ◽  
Band Gaps ◽  
Photoluminescence Spectra ◽  
Indirect Transition ◽  
Direct Transition ◽  
Direct Band Gap ◽  
Vis Spectroscopy ◽  
Direct Band

Thin films of CuSe2 nanoparticles embedded in selenium matrix were prepared by vacuum evaporation method on a glass substrate at room temperature. The optical properties of the films were investigated by photoluminescence spectroscopy (T=20-300K) and UV-VIS spectroscopy (T = 300K). Surface morphology was investigated by scanning electron microscopy. The band gap for direct transition in CuSe2 was found to be in the range of 2.72-2.75 eV and that for indirect transition is in the range of 1.71-1.75 eV determined by UV-VIS spectroscopy. On the other hand, selenium exhibits direct band gap in the range of 2.33-2.36 eV. All estimated band gaps slightly decrease with the increase of the film thickness. Photoluminescence spectra of the thin films clearly show emission bands at about 1.63 and 2.32 eV at room temperature, with no shift observed with decreasing temperature. A model was proposed for explaining such anomaly.

scholarly journals Penta-graphene: A new carbon allotrope

2015 ◽  
Vol 112 (8) ◽  
pp. 2372-2377 ◽  
Author(s):  
Shunhong Zhang ◽  
Jian Zhou ◽  
Qian Wang ◽  
Xiaoshuang Chen ◽  
Yoshiyuki Kawazoe ◽  
...  
Keyword(s):  
Band Gap ◽  
State Of The Art ◽  
Theoretical Calculations ◽  
Band Gaps ◽  
Ideal Strength ◽  
Atomic Configuration ◽  
Carbon Allotrope ◽  
Direct Band Gap ◽  
Direct Band ◽  
Negative Poisson's Ratio

A 2D metastable carbon allotrope, penta-graphene, composed entirely of carbon pentagons and resembling the Cairo pentagonal tiling, is proposed. State-of-the-art theoretical calculations confirm that the new carbon polymorph is not only dynamically and mechanically stable, but also can withstand temperatures as high as 1000 K. Due to its unique atomic configuration, penta-graphene has an unusual negative Poisson’s ratio and ultrahigh ideal strength that can even outperform graphene. Furthermore, unlike graphene that needs to be functionalized for opening a band gap, penta-graphene possesses an intrinsic quasi-direct band gap as large as 3.25 eV, close to that of ZnO and GaN. Equally important, penta-graphene can be exfoliated from T12-carbon. When rolled up, it can form pentagon-based nanotubes which are semiconducting, regardless of their chirality. When stacked in different patterns, stable 3D twin structures of T12-carbon are generated with band gaps even larger than that of T12-carbon. The versatility of penta-graphene and its derivatives are expected to have broad applications in nanoelectronics and nanomechanics.

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