Introduction of deep level impurities, S, Se, and Zn, into Si wafers for high-temperature operation of a Si qubit

To realize high-temperature operation of Si qubits, deep impurity levels with large confinement energy, which are hardly thermally excited, have been introduced into Si wafers. Group II impurity Zn and group VI impurities S and Se, which are known to form deep levels, were introduced into the Si substrates by ion implantation. These samples were analyzed for concentration-depth profiles, energy level depths, and absence of defects. To introduce deep impurities into thin channels such as 50-nm-thick Si, we found impurity introduction conditions so that the concentration depth profiles have maximum value at less than 50 nm from the Si surface. Then, the formation of the deep levels and absence of defects were experimentally examined. By using the conditions to introduce deep impurities into Si wafer obtained from the experiments, single-electron transport at room temperature, high-temperature operation of qubit, and room-temperature quantum magnetic sensors are promising.