Understanding the Transistor Behavior of Electron-Spin Qubits Above Cryogenic Temperatures

Electron-spin qubits are among the most promising platforms for the realization of a large-scale quantum computer. Physical limitations dictate their operation at cryogenic temperatures, in practice often well below 1 K. This requirement implies the employment of a refrigerator featuring long cooldown times and the need for die packaging, thereby strongly limiting the number of devices that can be measured simultaneously. In our work, we evaluate traditional transistor metrics to enable fast wafer-level screening of electron-spin qubit devices above cryogenic temperatures. To the best of our knowledge, a clear link between quantum dot metrics measured below 2 K and traditional transistor metrics measured at higher temperatures has not yet been identified. In this letter, we study the correlation between 10 mK measurements in the few-electron regime, and traditional transistor metrics at different temperatures. We observe a strong correlation up to 77 K, while correlations at higher temperatures are much less pronounced. We analyze this poor correlation via room-temperature TCAD simulations, showing that the underlying physics changes due to a considerable contribution of the substrate current to the device's off current above 77 K.