Multi-mode nanoFETs: From low power to high performance on demand

Abstract

Dynamic power management at the lowest design level of electronic hardware, i.e., at the device or transistor level, is still a novelty. Instead, energy saving is usually achieved at the circuit level by switching off high performance components and activating low leakage transistors in the current paths. We discuss here performance projections of field-effect transistors providing multiple power modes. A multi-mode (mm) FET can be configured from GHz performance to ultralow leakage by adjusting the charge injection into the transistor channel between thermionic and band- to-band tunnel injection. Nanodevices with ultrathin doping-free channels are the enabler of this novel device concept that requires excellent electrostatic control of the charge type and density. Moreover, nanomaterials with charge carriers of low effective mass will improve the mode tuning of mmFETs. TCAD simulations show that the device current can be switched through nine orders of magnitude at a supply voltage of 0.5V. The mmFET can also operate in a low dynamic power mode with reduced drive currents but delay times that still allow sub-MHz operation. These properties make mmFETs a promising technology for low power circuitry supplied only by energy harvesters. The possibility to further decrease the supply voltage by integrating a ferroelectric layer in the capacitor stack is also addressed.