08.02.2017 III-V Nanowire Heterostructures: From Materials to Advanced Devices

Dr. Gregor Koblmüller, Walter Schottky Institut, Technical University Munich (TUM)

Date: Wednesday, 15.02.2017, 16:00 h
Location: WZMW, Hans-Meerwein-Str. 6 (Lahnberge), seminar room 02D36

Abstract

Semiconductor nanowires (NW) comprise a unique class of low-dimensional nanostructures with very high aspect ratio, offering many interesting features in material design, novel fundamental properties and advanced device applications.

In this seminar, I will report our recent progress in the growth of III-V-semiconductor NWs on Si, their funda­mental structural, electronic and size quantization properties, and the realization of ultra-scaled NW-based electronic switches and monolithically integrated nanolasers on Si. A distinct feature of these III-V based NWs is their large sensitivity to detrimental surface states that often govern their electronic and optical pro­perties. We will therefore learn about surface-passivating core-shell NW heterostructures which are essential to inhibit surface scattering of charge carriers, suppress non-radiative surface recombination and further enable advanced schemes for carrier confinement and device functionality. Focusing mostly on the proto­typical GaAs-AlGaAs core-shell NW model system, I will demonstrate the possibility to realize optically highly active NWs even at extreme size limits below 10 nm (well below the de Broglie wavelength), where strong quantum confinement effects appear. Introduction of twin defects and small wurtzite inclusions give rise to crystal-phase quantum dots (CPQD) with sub-300 µeV linewidth, photon antibunching behavior and very short radiative lifetimes. The GaAs-AlGaAs core-shell NW heterostructures represent further a very useful system for nanolasers on Si photonic hardware. Here, we will see how through careful design one can fabri­cate vertical-cavity GaAs NW lasers on Si with remarkably high spontaneous coupling factors and ultrafast emission properties. Finally, I will present also ultra-scaled steep-slope electronic switches based on high-mobility modulation-doped GaAs-AlGaAs NW field effect transistors.