Mechanical Flip-Chip for Ultra-High Electron Mobility Devices

TL;DR

This paper introduces a mechanical flip-chip technique for fabricating electrostatic gates on high-mobility 2DEG devices, avoiding damage to the electron mobility typically caused by direct processing.

Contribution

It presents a novel flip-chip process that enables gate fabrication without processing the 2DEG material, preserving its ultra-high electron mobility.

Findings

Successfully fabricated quantum point contacts on ultra-high mobility GaAs/AlGaAs using the new method.

The technique preserves electron mobility better than traditional processing methods.

Applicable to various high-mobility 2DEG devices.

Abstract

Electrostatic gates are of paramount importance for the physics of devices based on high-mobility two-dimensional electron gas (2DEG) since they allow depletion of electrons in selected areas. This field-effect gating enables the fabrication of a wide range of devices such as, for example, quantum point contacts (QPC), electron interferometers and quantum dots. To fabricate these gates, processing is usually performed on the 2DEG material, which is in many cases detrimental to its electron mobility. Here we propose an alternative process which does not require any processing of the 2DEG material other than for the ohmic contacts. This approach relies on processing a separate wafer that is then mechanically mounted on the 2DEG material in a flip-chip fashion. This technique proved successful to fabricate quantum point contacts on both GaAs/AlGaAs materials with both moderate and ultra-high electron mobility.