High-Quality GaSe Single Crystal Grown by the Bridgman Method

Abstract

A high-quality GaSe single crystal was grown by the Bridgman method. The X-ray rocking curve for the studied GaSe sample is symmetric and the Full Width at Half Maximum (FWHM) is only 46 arcs, which is the smallest value ever reported for GaSe crystals. The IR-transmittance is about 66% in the range from 500 to 4000 cm−1. The photoluminescence spectrum at 9.2 K shows a symmetric and sharp excition peak in 2.1046 eV. The results indicate that the as-grown GaSe crystal is of high crystalline quality. The as-grown sans-serifε-GaSe crystal has a p-type conductance with the resistivity of 103 Ω/cm, and the Hall mobility is ~25 cm2 V−1 s−1. Few-layer GaSe crystals were prepared through mechanical exfoliation from this high-quality crystal sample. Few-layer GaSe-based photodetectors were fabricated, which exhibit an on/off ratio of 104, a field-effect differential mobility of 0.4 cm2 V−1 s−1, and have a fast response time less than 60 ms under light illumination.

Toward Air Stability of Thin GaSe Devices: Avoiding Environmental and Laser‐Induced Degradation by Encapsulation

“…The initial increase of photocurrent is also observed in a device measured in pure O 2 atmosphere, indicating that O 2 plays a critical role on the initial increase of the photocurrent. Indeed, according to our previous electronic probe microanalysis (EPMA) characterization, the atom ratio of Se and Ga is slightly smaller than 1 (Se:Ga = 49.5:50.5) in GaSe bulks, which indicates that the dominant defects in the pristine GaSe flakes are given by Se vacancies that may act as effective sites for O 2 adsorption. [9g,26]…”

“…Few‐layer GaSe flakes are fabricated by mechanical exfoliation in air with Nitto tape (SPV 224) of a bulk GaSe crystal, grown by the Bridgman method (see Figure a, bottom) . Figure a shows the lattice structure of GaSe where the different atomic planes bound by van der Waals forces are visible.…”

“…Sample Fabrication : Few‐layer GaSe flakes were mechanically exfoliated in air from an high‐quality bulk single crystals by using scotch tape and Nitto tape (Nitto Denko SPV 224) first and then onto a polydimethylsiloxane substrate (PDMS). After optical inspection, the selected flake was transferred from the PDMS to the pre‐patterned Au (60 nm)/SiO 2 (280 nm)/Si substrate (Ossila) as the photodetector devices and Raman samples by an all‐dry deterministic transfer method .…”

“…In this work, we present a study of the environmental and laser‐induced degradation of mechanically exfoliated GaSe flakes from a high‐quality GaSe bulk crystal . We combine optical microscopy, atomic force microscopy (AFM), Raman spectroscopy, and optoelectronic transport measurements on GaSe photodetector devices kept under different atmospheres (air, vacuum, O 2, and N 2 ) to study the influence of the degradation on the surface morphology and electronic and optical properties of few‐layer GaSe.…”

Insight into the electronic structure of semiconducting ε−GaSe and ε−InSe

“…MX compounds exhibit a direct band gap in the bulk [GaSe of about 2.0 eV [7] and InSe of about 1.3 eV [8] at room temperature (RT)], while they acquire an indirect band gap for few layers. Films of different thickness exhibit variable width of the band gap, thus they are optically active in the IR and visible region and are tested as active components in photodetectors [3,9,10]. Moreover, vertical van der Waals (vdW) heterostructures obtained by combining different twodimensional (2D) materials have been investigated in order to create novel functionalities [11][12][13][14][15], or to increase the carrier mobility [8,16].…”