Double Quantum Well Mediated Cold-Electron Injection to Si at Room Temperature

Thermally excited electrons following the Fermi-Dirac distribution typically degrade novel functionalities in electronic devices and mesoscopic systems. For example, it can wipe out the Coulomb blockade in single-electron transport at room temperature. It is also the root cause of the excessive heat dissipation of large-scale integrated circuits. Here we present an approach in which quantum well (QW) states selectively block the transport of thermally excited electrons, injecting only cold electrons to Si at room temperature. The cold-electron injection structure comprises 50 nm Cr (source), 2-4 nm Cr₂O₃ (QW1), 2-4 nm SnO_x (QW2, 1<x<2), 2 nm SiO₂, and p-type Si (drain). Electrons tunnel from the source to QW1, then to QW2, and to Si. Below a threshold voltage V_T (~2.5 V), the transverse momentum and energy conservation rules prohibit electron tunneling from QW1 to QW2, effectively blocking the transport of thermally excited electrons. At the threshold voltage V_T, where QW1 and QW2 energy levels align, electrons can tunnel from QW1 to QW2 as it fulfills both conservation rules. The I-V measurements show an abrupt current increase at V_T. The corresponding differential conductance (dI/dV) plots show extremely narrow peaks, with their FWHM only 0.025 mV, which corresponds to an effective electron temperature of ~0.1 K at room temperature. The capability of injecting cold electrons to Si at room temperature has the potential to be used for building energy-efficient electronic systems and tunnel transistors.