Light-induced transmission nonlinearities in gallium selenide

Abstract

The intensity of a He-Ne laser ͑633 nm, 5 mW͒ transmitted by different GaSe samples is observed to change in correlation with a Nd-yttrium-aluminum-garnet laser pulse ͑532 nm, 7.8 ns, 3 mJ͒ which excites them. Such time response has been attributed to a nonlinear optical effect, i.e., a decrease in the refractive index due to the exciton screening by the photogenerated carriers. A calculation of the absorption coefficient and refractive index at different carrier concentrations has led to a reconstruction of transmittance transients which fully agree with the experimental data at different incident intensities and temperatures.

Quantum size confinement in gallium selenide nanosheets: band gap tunability versus stability limitation

“…tive masses along the c-axis[23]. The results of these calculations are shown in figure 1(b), which seem to agree with the thickness dependence of the band gap of 2D GaSe obtained by more refined first-principles quantum mechanical calculations[29], at least in the range of thicknesses comprised in this work.…”

“…Very recently, other 2D semiconductors, these with more delocalized valence and conduction band states, have successfully extended the window of optical band gap values provided by 2D materials [20][21][22], although just reaching the low-energy side of the visible. Gallium selenide (GaSe), an indirect III-VI layered semiconductor with a 2.02 eV bandgap at room temperature [23], arises as one of the most promising candidates to extend even further the optical window of 2D materials with potential optoelectronic applications. On the one hand, GaSe nanosheets have been already used as photodetectors with high responsivity and high external quantum efficiency [24], as high-performance field-effect transistors [25], and in hybrid heterostructures giving rise to photodetectors that combine a high gain with a fast photoresponse [10,26].…”

“…the direct band gap energy and exciton binding energy in bulk GaSe at room temperature[23], respectively, d is the quantum well thickness, and m m ton reduced mass, as obtained from reported values of the electron m…”

Probing hyperbolic and surface phonon-polaritons in 2D materials using Raman spectroscopy

“… 31 , 32 and experimentally observed in GaSe for LO phonons 23 . The relatively large exciton binding in bulk GaSe (19.2meV) enables excitonic effects even at room temperature 33 , 34 . Figure 3 b presents Raman spectra from a 750-nm GaSe sample measured as a function of temperature (293 and 77 K) and laser excitation (532 and 633 nm).…”

Control of excitonic absorption by thickness variation in few-layer GaSe

“…The differential transmission signal is induced by the bandgap renormalization that causes a broadening and a shift of the excitonic transition. In addition, the photoexcitation of carriers reduces the probability for further probe photon absorption with a consequent bleaching signature that competes with the bandgap renormalization[22,23]. Differential transmission change of bulk GaSe at 4.2 K as a function of pump-probe time delay and probe wavelength.InFig.…”