title: GaN nanowire arrays with nonpolar sidewalls for vertically integrated field-effect transistors.
abstract: Vertically aligned gallium nitride (GaN) nanowire (NW) arrays have attracted a lot of attention because of their potential for novel devices in the fields of optoelectronics and nanoelectronics. In this work, GaN NW arrays have been designed and fabricated by combining suitable nanomachining processes including dry and wet etching. After inductively coupled plasma dry reactive ion etching, the GaN NWs are subsequently treated in wet chemical etching using AZ400K developer (i.e., with an activation energy of 0.69 ± 0.02 eV and a Cr mask) to form hexagonal and smooth a-plane sidewalls. Etching experiments using potassium hydroxide (KOH) water solution reveal that the sidewall orientation preference depends on etchant concentration. A model concerning surface bonding configuration on crystallography facets has been proposed to understand the anisotropic wet etching mechanism. Finally, NW array-based vertical field-effect transistors with wrap-gated structure have been fabricated. A device composed of 99 NWs exhibits enhancement mode operation with a threshold voltage of 1.5 V, a superior electrostatic control, and a high current output of >10 mA, which prevail potential applications in next-generation power switches and high-temperature digital circuits.
authors.affiliation: Institut für Halbleitertechnik (IHT), Technische Universität Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig, Germany. Laboratory for Emerging Nanometrology (LENA), Technische Universität Braunschweig, Langer Kamp 6, D-38106 Braunschweig, Germany.
authors.forename: Feng
authors.initials: F
authors.lastname: Yu
authors.forename: Shengbo
authors.initials: S
authors.lastname: Yao
authors.forename: Friedhard
authors.initials: F
authors.lastname: Römer
authors.forename: Bernd
authors.initials: B
authors.lastname: Witzigmann
authors.forename: Tilman
authors.initials: T
authors.lastname: Schimpke
authors.forename: Martin
authors.initials: M
authors.lastname: Strassburg
authors.forename: Andrey
authors.initials: A
authors.lastname: Bakin
authors.forename: Hans Werner
authors.initials: HW
authors.lastname: Schumacher
authors.forename: Erwin
authors.initials: E
authors.lastname: Peiner
authors.forename: Hutomo Suryo
authors.initials: HS
authors.lastname: Wasisto
authors.forename: Andreas
authors.initials: A
authors.lastname: Waag