Ballistic electronics: breaking the barrier in terahertz speed processing

Abstract

Novel device called the Ballistic Deflection Transistor (BDT) is presented. BDT is a unique planar device that possesses both a positive and a negative transconductance region and is capable of operating into the THz frequency regime at the room temperature. BDT is based upon an electron steering and a ballistic deflection effect. Modeling and experimental measurements have indicated that the transconductance of the device increases with applied drain-source voltage. The differential mode of operation provides two drain outputs, which depending on the gate bias, are either complementary or non-complementary. The latter facilitates a wide variety of circuit design techniques. The extremely low gate capacitance of the BDT planar structure predicts THz performance. We present measured results from the fabrication of a BDT NAND gate and other BDT gate structures. The measured results in the quasi-ballistic regime are further supported by an empirical model generated from a fabricated BDT output response. Future plans to facilitate large-scale integration are also discussed. Our Monte Carlo analysis reports on the effect of different geometry parameters on the transfer characteristics. The strength of the gate control in the InGaAs channel is analyzed. We propose different models for the surface charge density to explain the observed experimental measurements. Finally, we present our time-domain spectroscopy studies used to successfully demonstrate a THz response of ballistic nanodevices at room temperature, excited by picosecond electrical pulses.