Low percolation density and charge noise with holes in germanium

We engineer planar Ge/SiGe heterostructures for low disorder and quiet hole quantum dot operation by positioning the strained Ge channel 55 nm below the semiconductor/dielectric interface. In heterostructure field effect transistors, we measure a percolation density for two-dimensional hole transport of 2.1 × 1010 cm−2, indicative of a very low disorder potential landscape experienced by holes in the buried Ge channel. These Ge heterostructures support quiet operation of hole quantum dots and we measure an average charge noise level of SĒ=0.6μeV/Hz at 1 Hz, with the lowest level below our detection limit SE=0.2μeV/Hz. These results establish planar Ge as a promising platform for scaled two-dimensional spin qubit arrays.