Increased-Functionality VLSI-Compatible Devices Based on Backward-Diode Floating-Base Si/SiGe Heterojunction Bipolar Transistors

Abstract

As modern semiconductor circuits progress towards greater complexity and ever smaller feature sizes at ever greater processing cost, increasing the functionality of logic devices is becoming a primary direction in microelectronics research and development. Several classes of semiconductor devices promising higher functionality than standard transistor logic have been intensively studied over the past decade, including multiterminal real-space transfer¹ and resonant tunneling² heterostructures. However, the vast majority of these devices were based on the bandgap engineering possibilities of compound semiconductor heterostructures and required low temperatures for effective operation, making them ill-suited for current digital technology. Recently, there has been a demonstration of a class of increased functionality devices based on multi-emitter heterojunction bipolar transistor (HBT’s) fabricated in the InGaAs/InP material system.³ We propose to investigate the performance of an analogous, multi-terminal backward-diode HBT structures in the Si/SiGe material system,⁴ which would utilize the advantageous properties of Si/SiGe heterojunctions and, more importantly, would feature full compatibility with the silicon technology that will dominate microelectronics for the foreseeable future.