Electron transport in gated InGaAs and InAsP quantum well wires in selectively-grown InP ridge structures

TL;DR

This study fabricates and characterizes InGaAs and InAsP quantum well wires embedded in InP ridge structures, demonstrating their potential for quantum dot applications through transport measurements and gate control.

Contribution

It introduces a method for fabricating gated quantum well wires in InP ridges and investigates their transport properties, including quantum dot formation.

Findings

Reproducible mesoscopic conductance fluctuations at low temperatures

Non-leaky gating with good pinch-off characteristics

Observation of Coulomb blockade oscillations indicating quantum dot formation

Abstract

The purpose of this work is to fabricate ribbon-like InGaAs and InAsP wires embedded in InP ridge structures and investigate their transport properties. The InP ridge structures that contain the wires are selectively grown by chemical beam epitaxy (CBE) on pre-patterned InP substrates. To optimize the growth and micro-fabrication processes for electronic transport, we explore the Ohmic contact resistance, the electron density, and the mobility as a function of the wire width using standard transport and Shubnikov-de Haas measurements. At low temperatures the ridge structures reveal reproducible mesoscopic conductance fluctuations. We also fabricate ridge structures with submicron gate electrodes that exhibit non-leaky gating and good pinch-off characteristics acceptable for device operation. Using such wrap gate electrodes, we demonstrate that the wires can be split to form quantum dots evidenced by Coulomb blockade oscillations in transport measurements.