Trapping photo-carriers in undoped gate-defined quantum dots using an on-chip microwave resonator for charge readout
Scaling up gate-defined quantum dot systems is hindered by the rapid growth in the number of control gates. To tackle this challenge, we propose a different approach where the quantum dots are created from optically generated charges trapped beneath accumulation gates. By shining an above-the-gap laser light onto an undoped GaAs substrate, we demonstrate that it is possible to create and separate electron-hole pairs to form quantum dots. For the charge readout, we use a superconducting coplanar waveguide resonator capacitively coupled to the quantum dots. With these elements, we demonstrate a working many-charge double quantum dot device comprised of only two plunger gates, one tunnel coupling gate and one sensing gate. With our approach, we show that populating quantum dots does not require engineered reservoirs, source/drain bias, ohmic contacts, or in-situ doping. As a result, the number of gates can be kept minimal and the fabrication process can be simplified. Moreover, this approach can be applied to a wide range of direct-bandgap semiconductor quantum dot systems. This hybrid device demonstration is a first step towards a different scalability approach for quantum dot arrays.