Electronic structure of III-V broken gap materials and terminal control in three dimensional nano-scale MOSFETs.

摘要

In the past few years InAs-Sb/GaSb type-II superlattice have been grown and their performance has been evaluated in great details due to their applications in realization of high performance infrared detectors. They offer number of advantages over other technologies since they possess large effective mass which reduces tunneling, have reduced Auger recombination process, energy gap tunability and uniformity. The performance of detectors based on such superlattices is directly related to the fundamental carrier transport physics. Because of the spatial regularity, electrical properties of these materials are determined by the carrier distribution close to the band edges of the fundamental energy gap and hence accurately calculating the bandstructure is key step in analyzing them. Moreover the absorber region of the detector is thick and simulating it can be computationally expensive. A novel method is presented with which we can model the absorber region as an effective material and reduce significantly the computational cost of modeling the structure.;The progress of the silicon integrated-circuit industry, due to scaling the device dimensions, is well known. However, this down-scaling has made it increasingly difficult to maintain acceptable transistor performance. The electrical characteristics of down-scaled planar transistors are degraded by short-channel effects. The leading solution to the problems of planar transistors is to adopt a three-dimensional structure. A novel computational technique is presented to study the terminal influence inside the three-dimensional (3D) nano-scale MOSFET using TCAD simulations. Within the MOSFET we can take the derivative of the electrostatic potential with respect to voltages at each terminal, and when these derivatives are added together they always sum to unity. We have found that these functions, which we refer to as terminal influence functions or control functions, can be used to quantify the relative influence or control of the terminals anywhere inside the MOSFET, including the channel. The motivation for moving from planar MOSFETs to 3D-MOSFETs is to increase the gate control over the channel. The terminal influence functions quantify the notion of control. To gain insight into the working of a semiconductor device we may visualize different quantities like potential, charge or current density etc. These quantities are available in the standard TCAD tool-kit, but do not directly address the mechanism of terminal control. Terminal influence functions do this very clearly.