title: WSe₂ Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature.
abstract: Monolayers of molybdenum and tungsten dichalcogenides are direct bandgap semiconductors, which makes them promising for optoelectronic applications. In particular, van der Waals heterostructures consisting of monolayers of MoS2 sandwiched between atomically thin hexagonal boron nitride (hBN) and graphene electrodes allows one to obtain light emitting quantum wells (LEQWs) with low-temperature external quantum efficiency (EQE) of 1%. However, the EQE of MoS2- and MoSe2-based LEQWs shows behavior common for many other materials: it decreases fast from cryogenic conditions to room temperature, undermining their practical applications. Here we compare MoSe2 and WSe2 LEQWs. We show that the EQE of WSe2 devices grows with temperature, with room temperature EQE reaching 5%, which is 250× more than the previous best performance of MoS2 and MoSe2 quantum wells in ambient conditions. We attribute such different temperature dependences to the inverted sign of spin-orbit splitting of conduction band states in tungsten and molybdenum dichalcogenides, which makes the lowest-energy exciton in WSe2 dark.
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.|National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: F
authors.initials: F
authors.lastname: Withers
authors.affiliation: School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K.
authors.forename: O
authors.initials: O
authors.lastname: Del Pozo-Zamudio
authors.affiliation: School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K.
authors.forename: S
authors.initials: S
authors.lastname: Schwarz
authors.affiliation: School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K.
authors.forename: S
authors.initials: S
authors.lastname: Dufferwiel
authors.affiliation: School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K.
authors.forename: P M
authors.initials: PM
authors.lastname: Walker
authors.affiliation: School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K.
authors.forename: T
authors.initials: T
authors.lastname: Godde
authors.affiliation: School of Materials, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: A P
authors.initials: AP
authors.lastname: Rooney
authors.affiliation: School of Materials, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Gholinia
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: C R
authors.initials: CR
authors.lastname: Woods
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.|National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: P
authors.initials: P
authors.lastname: Blake
authors.affiliation: School of Materials, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: S J
authors.initials: SJ
authors.lastname: Haigh
authors.affiliation: National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.|Physics Department, Columbia University , New York, New York 10027, United States.
authors.forename: I L
authors.initials: IL
authors.lastname: Aleiner
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: A K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.|National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: V I
authors.initials: VI
authors.lastname: Fal'ko
authors.affiliation: School of Physics and Astronomy, University of Sheffield , Sheffield, S3 7RH, U.K.
authors.forename: A I
authors.initials: AI
authors.lastname: Tartakovskii
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.|National Graphene Institute, University of Manchester , Oxford Road, Manchester, M13 9PL, U.K.
authors.forename: K S
authors.initials: KS
authors.lastname: Novoselov
keywords: Electroluminescence; graphene; hexagonal boron nitride; photoluminescence; transition metal dichalcogenides; tungsten diselenide; van der Waals heterostructure