title: Electrical and optical properties of InP nanowire ensemble p⁺-i-n⁺ photodetectors.
abstract: We report on a comprehensive study of electrical and optical properties of efficient near-infrared p⁺-i-n⁺ photodetectors based on large ensembles of self-assembled, vertically aligned i-n⁺ InP nanowires monolithically grown on a common p⁺ InP substrate without any buffer layer. The nanowires have a polytype modulated crystal structure of wurtzite and zinc blende. The electrical data display excellent rectifying behavior with an ideality factor of about 2.5 at 300 K. The ideality factor scales with 1/T, which possibly reflects deviations from classical transport models due to the mixed crystal phase of the nanowires. The observed dark leakage current is of the order of merely ∼100 fA/nanowire at 1 V reverse bias. The detectors display a linear increase of the photocurrent with reverse bias up to about 10 pA/nanowire at 5 V. From spectrally resolved measurements, we conclude that the photocurrent is primarily generated by funneling photogenerated carriers from the substrate into the NWs. Contributions from direct excitation of the NWs become increasingly important at low temperatures. The photocurrent decreases with temperature with an activation energy of about 50 meV, which we discuss in terms of a temperature-dependent diffusion length in the substrate and perturbed transport through the mixed-phase nanowires.
authors.affiliation: Laboratory of Mathematics, Physics and Electrical Engineering, Halmstad University, Box 823, SE-30118 Halmstad, Sweden. hakan.pettersson@hh.se
authors.forename: Håkan
authors.initials: H
authors.lastname: Pettersson
authors.forename: Irina
authors.initials: I
authors.lastname: Zubritskaya
authors.forename: Ngo Tuan
authors.initials: NT
authors.lastname: Nghia
authors.forename: Jesper
authors.initials: J
authors.lastname: Wallentin
authors.forename: Magnus T
authors.initials: MT
authors.lastname: Borgström
authors.forename: Kristian
authors.initials: K
authors.lastname: Storm
authors.forename: Lars
authors.initials: L
authors.lastname: Landin
authors.forename: Peter
authors.initials: P
authors.lastname: Wickert
authors.forename: Federico
authors.initials: F
authors.lastname: Capasso
authors.forename: Lars
authors.initials: L
authors.lastname: Samuelson