Direct Band-gap Electroluminescence from Strained n-Ge Light Emitting Diodes

AbstractIn atomically thin transition metal dichalcogenide semiconductors, there is a crossover from indirect to direct band gap as the thickness drops to one monolayer, which comes with a fast increase of the photoluminescence signal. Here, we show that for different alloy compositions of WS2(1−x)Se2x this trend may be significantly affected by the alloy content and we demonstrate that the sample with the highest Se ratio presents a strongly reduced effect. The highest micro-PL intensity is found for bilayer WS2(1−x)Se2x (x = 0.8) with a decrease of its maximum value by only a factor of 2 when passing from mono-layer to bi-layer. To better understand this factor and explore the layer-dependent band structure evolution of WS2(1−x)Se2x, we performed a nano-angle-resolved photoemission spectroscopy study coupled with first-principles calculations. We find that the high micro-PL value for bilayer WS2(1−x)Se2x (x = 0.8) is due to the overlay of direct and indirect optical transitions. This peculiar high PL intensity in WS2(1−x)Se2x opens the way for spectrally tunable light-emitting devices.

Download Full-text

Growth and analysis of a direct band-gap light-emitting structure on gallium phosphide

Conference Proceedings LEOS'96 9th Annual Meeting IEEE Lasers and Electro-Optics Society ◽

10.1109/leos.1996.571585 ◽

2002 ◽

Author(s):

Jong-Won Lee ◽

A. Schremer ◽

D. Fekete ◽

J. Ballantyne

Keyword(s):

Band Gap ◽

Gallium Phosphide ◽

Light Emitting ◽

Direct Band Gap ◽

Direct Band

Download Full-text

Ge and GeSn Light Emitters on Si

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.242.353 ◽

2015 ◽

Vol 242 ◽

pp. 353-360

Author(s):

Michael Oehme ◽

Martin Gollhofer ◽

Konrad Kostecki ◽

Roman Koerner ◽

Stefan Bechler ◽

...

Keyword(s):

Room Temperature ◽

Light Emitting Diodes ◽

Optical Feedback ◽

Heteroepitaxial Growth ◽

Light Emitters ◽

Light Emitting ◽

Direct Band Gap ◽

Si Substrates ◽

Direct Band ◽

Clear Shift

The heteroepitaxial growth of GeSn and Ge crystals on Si substrates are investigated for Si-based photonic applications. Light Emitting Diodes with emission wavelengths from 2,100 to 1,550 nm could be demonstrated with active intrinsic GeSn light emitting layers between Ge barriers. A clear shift of the direct band gap toward the infrared beyond 2 μm is measured. Emission intensity is increased compared to Ge Light Emitting Diodes. Room temperature lasing from electrically pumped n-type doped Ge edge emitting devices are demonstrated. The edge emitter is formed by cleaving Si-Ge waveguide heterodiodes, providing optical feedback through a Fabry-Pérot resonator. The electroluminescence spectra of the devices showed optical bleaching and intensity gain for wavelengths between 1,660 nm and 1,700 nm.

Download Full-text

Development of Direct Band Gap Group IV Semiconductors with the Incorporation of Sn

10.21236/ada558773 ◽

2012 ◽

Author(s):

Hung Hsiang Cheng

Keyword(s):

Band Gap ◽

Group Iv ◽

Direct Band Gap ◽

Group Iv Semiconductors ◽

Direct Band

Download Full-text

Analysis of Direct Band Gap A2ScInI6 (A=Rb, Cs) Double Perovskite Halides Using DFT Approach for Renewable Energy Devices

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2021.05.080 ◽

2021 ◽

Author(s):

N.A. Noor ◽

M. Waqas Iqbal ◽

Taharh Zelai ◽

Asif Mahmood ◽

H.M. Shaikh ◽

...

Keyword(s):

Renewable Energy ◽

Band Gap ◽

Double Perovskite ◽

Energy Devices ◽

Direct Band Gap ◽

Direct Band

Download Full-text

Optical Studies of Poly (N-Carbazole) (PVK) Blending with Polyvinylpyrrolidone (PVP) Using Tauc/Davis-Mott Model

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.527 ◽

2013 ◽

Vol 652-654 ◽

pp. 527-531 ◽

Cited By ~ 1

Author(s):

A.N. Alias ◽

T.I. Tunku Kudin ◽

Z.M. Zabidi ◽

M.K. Harun ◽

Ab Malik Marwan Ali ◽

...

Keyword(s):

Band Gap ◽

Urbach Energy ◽

Quartz Substrate ◽

Optical Studies ◽

Direct Band Gap ◽

Mott Model ◽

Blended Polymer ◽

Electronic Parameters ◽

Direct Band ◽

Indirect Band Gap

The optical absorption spectra of blended poly (N-carbazole) (PVK) with polyvinylpyrrolidone (PVP) in various compositions are investigated. A doctor blade technique was used to coat the blended polymer on a quartz substrate. The electronic parameters such as absorption edge (Ee), allowed direct band gap (Ed), allowed indirect band gap (Ei), Urbach edge (Eu) and steepness parameter (γ) were calculated using Tauc/Davis-Mott Model. The results reveal that the Ee, Ed and Ei increase with increasing of PVP ratio. There also have variation changing in Urbach energy and steepness parameter.

Download Full-text