Direct and indirect band gaps

About: Direct and indirect band gaps is a research topic. Over the lifetime, 10940 publications have been published within this topic receiving 327355 citations.

Interfaces of ZnO Nanowires Grown on Semiconducting Surfaces

Abstract: The large direct band gap of ZnO makes it an important semiconductor. ZnO can be grown in the form of nanowires on various substrates, which makes it a potential candidate for nanoparticle-based device applications such as heterojunction solar cells. Aligned nanowires of ZnO can be grown on semiconductor surfaces to make p–n junctions. The characteristics and performance of devices are critically dependant on the alignment, distribution and the nanowire–substrate interface character. While various methods to control the alignment and distribution of ZnO nanowire on different surfaces have been reported in the literature [1], the structure of the interface between the ZnO nanowire and the semiconducting surface is almost unknown. The motivation of this work is to characterize the interface of ZnO nanowires grown on a Si surface.

Effect of rotation on photonic band gap of two-dimensional square lattice photonic crystal with hollow rod

Abstract: The plane-wave expansion method is used to calculate TE and TM mode band gaps for two-dimensional square lattice photonic crystal with hollow anisotropic tellurium (Te) rods under three different rotation operations. The effect of rotation on TE and TM mode band gaps and absolute band gap is investigated. The calculated results show that the high order band gaps of TM mode have a close relationship with structure rotation symmetry, and the rotation symmetry and the distribution of Te in x - y plane together influence TE mode band gaps.

Distributed feedback semiconductor laser oscillating at longer wavelength mode and its manufacture method

Abstract: A lower quantum well structure is formed extending along a resonator direction, the lower quantum well structure being formed by alternately stacking lower barrier layers and lower well layers having a band gap narrower than a band gap of the lower barrier layers. An intermediate layer is disposed over the lower quantum well structure. The intermediate layer has a band gap broader than the band gap of the lower barrier layers. An upper quantum well structure is periodically disposed over the intermediate layer along the resonator direction. The upper quantum well structure is formed by alternately stacking upper well layers and upper barrier layers having a band gap broader than a band gap of the upper well layers. A distributed feedback semiconductor laser is provided which is not likely to oscillate in the mode at a shorter wavelength and is likely to oscillate in the mode at a longer wavelength.

Influence of Optical Excitation of Two-Dimensional Surface Subbands on Photocurrent across Semiconductor-Electrolyte Interface

Abstract: It was shown that in the case of TiO2 contacted with an electrolyte, optical transitions of electrons from the valence band to the two-dimensional surface subband located near the conduction band or covered with the band.

Effect of substrate screening on the electronic structure of monolayer MoS2

Abstract: Monolayers of transition-metal dichalcogenides (TMD) hold great promise as future nanoelectronic and optoelectronic devices. An essential feature for achieving high device performance is the use of suitable supporting substrates, which can strongly affect the electronic and optical properties of these two-dimensional (2D) materials. Here, we investigate the effect of substrate screening on the quasiparticle band structure of monolayer MoS2 by performing many-body GW calculations with an effective dielectric screening. We show that the substrate can have a significant effect on the quasiparticle band gap, for example the gap renormalization is as large as 250 meV for MoS2 on SiO2. Within the G0W0 approximation, we find that the supported monolayer exhibits a direct band gap, in contrast to the free-standing monolayer. We also find that substrate screening induces an enhancement of the carrier effective masses by as much as 27% for holes, shifts plasmon satellites, and redistributes quasiparticle weight. Our results highlight the importance of the dielectric environment in the design of 2D TMD-based devices.