Direct Observation of Band Gap Renormalization in Layered Indium Selenide

Abstract

Manipulation of intrinsic electronic structures by electron or hole doping in a controlled manner in van der Waals layered materials is the key to control their electrical and optical properties. Two-dimensional indium selenide (InSe) semiconductor has attracted attention due to its direct band gap and ultrahigh mobility as a promising material for optoelectronic devices. In this work, we manipulate the electronic structure of InSe by in situ surface electron doping and obtain a significant band gap renormalization of ∼120 meV directly observed by high-resolution angle resolved photoemission spectroscopy. This moderate doping level (carrier concentration of 8.1 × 1012 cm–2) can be achieved by electrical gating in field effect transistors, demonstrating the potential to design of broad spectral response devices.

Ultrafast dynamics with time-resolved ARPES: photoexcited electrons in monochalcogenide semiconductors

“…The overall energy resolution of the experiment is ∼ =30 meV and the cross correlation between pump and probe pulses has full width at half maximum (FWHM) of 150 fs. High-quality single crystals of InSe (doped with Sn, 0.01%) we used have been grown using the Bridgmann method from a nonstoichiometric melt [11]. High-quality single crystal of GeSe was purchased from company of HQ graphene.…”

“…ARPES is the most direct way to observe the electronic structure of a semiconductor with high energy and momentum resolution. For example, the electronic structure of indium selenide (InSe) has been directly observed by ARPES in a previous study, and it shows out-of-plane dispersions by changing photon energy, which indicates a quasi-two dimensional nature of the bulk material; in addition, if the electronic structure of InSe is modified with surface alkali atoms doping, the observed ∼1.3 eV band gap in bulk InSe is subsequently reduced as function of doping [11].…”

Ultrafast dynamics of hot carriers in a quasi–two-dimensional electron gas on InSe

“…The choice of polar material is motivated by the fact that InSe is one of the best van der Waals structures for the fabrication of FET devices 15,16 . It has an electronic gap comparable to silicon 17 , small effective mass 18 , layered structure 19 and carrier mobility higher than transition metal dichalcogenides 16 . The electronic state and distribution function of hot electrons in the accumulation layer is directly monitored by time and angle resolved photoelectron spectroscopy (tr-ARPES).…”

“…The ρ M value is comparable to the maximal doping level achieved via electrostatic gating 16 . At even higher alkali concentration the surface of InSe becomes unstable and the quasi-2DEG disappears 17 .…”

Phase transition and thermal stability of epitaxial PtSe2 nanolayer on Pt(111)

“…In particular, the rapid advances in graphene and silicene research [1][2][3][4][5] have led to considerable interest in other types of 2D systems such as germanene, phosphorene, boron nitride and transition metal dichalchogenide (TMD) layers. [6][7][8][9][10] In addition to chemical composition, atomic arrangement and dimension proved to be one of the most important parameters in determining lm properties and device performance. 2D layer materials, especially in the monolayer limit, have aroused enormous attention because they exhibit interesting novel properties that are rather different from those of the bulk phase.…”