Impact of biased cooling on the operation of undoped silicon quantum well field-effect devices for quantum circuit applications

TL;DR

This study investigates how biased cooling affects undoped silicon quantum well devices, revealing that it introduces a static electric field that influences device operation without degrading key quality features, thus offering new control options for quantum circuits.

Contribution

The paper demonstrates that biased cooling induces a static electric field in undoped SiGe/Si/SiGe quantum wells, expanding the tunability of 2DEG properties without compromising device quality.

Findings

Biased cooling creates a static electric field superimposed on gate voltage.

The voltage operation window for 2DEG can be widened via biased cooling.

Device quality features like mobility remain unaffected by biased cooling.

Abstract

Gate-tunable semiconductor nanosystems are getting more and more important in the realization of quantum circuits. While such devices are typically cooled to operation temperature with zero bias applied to the gate, biased cooling corresponds to a non-zero gate voltage being applied before reaching the operation temperature. We systematically study the effect of biased cooling on different undoped SiGe/Si/SiGe quantum well field-effect stacks (FESs), designed to accumulate and density-tune two-dimensional electron gases (2DEGs). In an empirical model, we show that biased cooling of the undoped FES induces a static electric field, which is constant at operation temperature and superimposes onto the field exerted by the top gate onto the 2DEG. We show that the voltage operation window of the field-effect-tuned 2DEG can be chosen in a wide range of voltages via the choice of the biased cooling voltage. Importantly, quality features of the 2DEG such as the mobility or the temporal stability of the 2DEG density remain unaltered under biased cooling. We discuss how this additional degree of freedom in the tunability of FESs may be relevant for the operation of quantum circuits, in particular for the electrostatic control of spin qubits.