Electronic band structure of GaSe(0001):  Angle-resolved photoemission and<i>ab initio</i>theory

The structure and temperature dependent spectral photoconductivity of as-grown and N-and Si-implanted GaSe single crystals have been studied. It was observed that post-annealing results in a complete recovery of the crystalline nature that was moderately reduced upon implantation. The band edge is shifted in the implanted sample which is attributed to the structural modifications and continuous shallow levels introduced upon implantation and annealing. Our calculations showed that the trap density is increased upon implantation and annealing which confirms a possibility of explanation the phenomenon within a framework of continuous trap levels. Photocurrent measurements as a function of photo-excitation intensity also support continuous distribution of localized states in the band gap.

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“…GaSe is a direct band-gap material [19] and the absorption mechanism near the bandgap energy values is mainly due to allowed direct transition.…”

Section: Resultsmentioning

confidence: 99%

Influence of ion implantation on structural and photoconductive properties of Bridgman grown GaSe single crystals

Karabulut¹,

Parlak

Turan

et al. 2006

Cryst. Res. Technol.

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“…The ε polytype of GaSe was considered in recent DFT calculations of Refs. [28,29]. To our knowledge, the effect of pressure on the band structure of the ε polytype has not been calculated before, except for the band structure at 7 GPa given in Ref.…”

Section: Electronic Structure Of E-gase Under Pressurementioning

confidence: 98%

“…As for layered GaSe at ambient pressure, ab initio methods have been employed in lattice dynamics calculations [25] and in the interpretation of photoemission experiments [28,29]. It appears that fully relaxed ab initio calculations of the pressure-dependent structural or dynamical properties of layered GaSe have not been reported so far.…”

Section: Constrained Structure Optimizationmentioning

confidence: 99%

Effect of pressure on the structural properties and electronic band structure of GaSe

Schwarz

Olguı́n

Cantarero

et al. 2006

Physica Status Solidi (b)

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The structural properties of GaSe have been investigated up to 38 GPa by monochromatic X-ray diffraction. The onset of the phase transition from the ε -GaSe to a disordered NaCl-type structural motif is observed near 21 GPa. Using the experimentally determined lattice parameters of the layered ε -phase as input, constrained ab-initio total energy calculations were performed in order to optimize the internal structural parameters at different pressures. The results obtained for the nearest-neighbor Ga -Se distance agree with those derived from recent EXAFS measurements. In addition, information is obtained on the changes of Ga -Ga and Se -Se bond lengths which were not accessible to a direct experimental determination yet. Based on the optimized structural parameters, we report calculations of band gap changes of ε -GaSe under pressure. The optical response and electronic band structure of the metallic high-pressure phase of GaSe are discussed briefly.

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“…24, 25 The in-plane geometry of monolayer GaSe is a honeycomb structure in which Ga and Se atoms respectively occupy the two sublattices ( Figure 1b). In multilayer GaSe, the adjacent monolayers are coupled by van der Waals interactions.…”

mentioning

confidence: 99%

Strong Second-Harmonic Generation in Atomic Layered GaSe

Zhou¹,

Cheng

Zhou³

et al. 2015

J. Am. Chem. Soc.

300

259

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Nonlinear effects in two-dimensional (2D) atomic layered materials have recently attracted increasing interest. Phenomena such as nonlinear optical edge response, chiral electroluminescence, and valley and spin currents beyond linear orders have opened up a great opportunity to expand the functionalities and potential applications of 2D materials. Here we report the first observation of strong optical second-harmonic generation (SHG) in monolayer GaSe under nonresonant excitation and emission condition. Our experiments show that the nonresonant SHG intensity of GaSe is the strongest among all the 2D atomic crystals measured up to day. At the excitation wavelength of 1600 nm, the SHG signal from monolayer GaSe is around 1-2 orders of magnitude larger than that from monolayer MoS2 under the same excitation power. Such a strong nonlinear signal facilitates the use of polarization-dependent SHG intensity and SHG mapping to investigate the symmetry properties of this material: the monolayer GaSe shows 3-fold lattice symmetry with an intrinsic correspondence to its geometric triangular shape in our growth condition; whereas the bilayer GaSe exhibits two dominant stacking orders: AA and AB stacking. The correlation between the stacking orders and the interlayer twist angles in GaSe bilayer indicates that different triangular GaSe atomic layers have the same dominant edge configuration. Our results provide a route toward exploring the structural information and the possibility to observe other nonlinear effects in GaSe atomic layers.

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Electronic band structure of GaSe(0001): Angle-resolved photoemission andab initiotheory

Cited by 66 publications

References 31 publications

Influence of ion implantation on structural and photoconductive properties of Bridgman grown GaSe single crystals

Influence of ion implantation on structural and photoconductive properties of Bridgman grown GaSe single crystals

Effect of pressure on the structural properties and electronic band structure of GaSe

Strong Second-Harmonic Generation in Atomic Layered GaSe

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