Mechanical Flip-Chip for Ultra-High Electron Mobility Devices

Keyan Bennaceur,John L Reno,Loren N Pfeiffer,Samuel Gaucher,Guillaume Gervais,Dominique Laroche,Benjamin A Schmidt,Ken W West,Michael P Lilly

doi:10.1038/srep13494

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.

Highlights

Lineage[10], but their small energy many-body gaps of ~500 mK and 50 mK, respectively, is affected by disorder of any kind
In order to circumvent the problem of degradation of the electronic mobility, we have developed a flip-chip technique where all processing steps required to fabricate the electrostatic gates are performed on a separate substrate that is mounted on the surface of the 2DEG
The gates are fabricated directly on top of the 2DEG material using a combination of e-beam and optical lithography

Summary

Methods

In order to circumvent the problem of degradation of the electronic mobility, we have developed a flip-chip technique where all processing steps required to fabricate the electrostatic gates are performed on a separate substrate that is mounted on the surface of the 2DEG. Since several types of gated devices have active areas of a few μm[2] only, should the need arise, our approach allows for the device to be remounted on a slightly different part of the wafer This technique allows one to swap gates so as to measure different devices (or designs) on the exact same piece of material. It avoids wasting precious material during low-yield processes, which is common when fabricating complex devices

Results

Author Contributions

Additional Information