Anthony Martinez1,Pushkar Gothe1,Ojas Bhayde1,J. Tyler Gish2,M. R. Tiscareno1,Jiechao Jiang1,Joseph Ngai1,Efstathios Meletis1,Mark Hersam2,Seong Jin Koh1
The University of Texas at Arlington1,Northwestern University2
Anthony Martinez1,Pushkar Gothe1,Ojas Bhayde1,J. Tyler Gish2,M. R. Tiscareno1,Jiechao Jiang1,Joseph Ngai1,Efstathios Meletis1,Mark Hersam2,Seong Jin Koh1
The University of Texas at Arlington1,Northwestern University2
The root cause of the excessive power consumption (or excessive heat dissipation) of modern large-scale integrated circuits is the intrinsic thermal excitation of electrons that follows the Fermi-Dirac distribution. The hot electrons at the Fermi-Dirac distribution tail overcomes the OFF-state energy barrier of transistors, leading to inadvertent large electron flows and thereby large OFF-state power consumption. Here we represent an approach in which thermally exited electrons are filtered by a quantum well (QW) state and only energy-filtered cold electrons are injected to semiconductor conduction band. We demonstrate that the energy filtering enables transport of extremely cold electrons, whose effective electron temperature can reach as low as 7 Kelvin at room temperature. The electron energy filtering structure was fabricated on a wafer scale using CMOS-compatible processes and materials. The energy filtering stack is composed of source metal (Cr), first tunneling barrier (0.5-1 nm Al<sub>2</sub>O<sub>3</sub> or Si<sub>3</sub>N<sub>4</sub>), QW layer (1-5 nm SnO<sub>2</sub> or 2 nm Cr<sub>2</sub>O<sub>3</sub>), second tunneling barrier (1.5-2 nm SiO<sub>2</sub>), and Si. Electrons are tunneled from the source to a QW state, and then energy-filtered cold electrons are tunneled from the QW state to Si conduction band. Room-temperature current-voltage (I-V) measurements showed extremely abrupt current jumps, which correspond to alignments of the QW levels with the conduction band edge of Si. Differential conductance (dI/dV) plots show narrow peaks, with their FWHMs (full widths at half maximum) only ~2 mV, corresponding to an effective electron temperature of 7 Kelvin at room temperature. This cold-electron injection demonstrated for a Si system has a potential to realize steep subthreshold swing of much less than 60 mV/decade at room temperature, leading to energy-efficient low-power transistors.<br/><br/>This work was supported by the National Science Foundation UTA/NU Partnership for Research and Education in Materials (NSF DMR-2122128). The atomic layer deposition work was supported by the National Science Foundation Materials Research Science and Engineering Center at Northwestern University (NSF DMR-1720139). S.J.K. also gratefully acknowledges support from the National Science Foundation RAPID program (NSF ECCS-2031770).