Mobility and Device Applications of Heavily Doped Silicon and Strained SILICON(1X) Germanium(x) Layers
Abstract
With the advent of Si molecular beam epitaxy (Si MBE), a significant amount of research has occurred to seek alternative high conductivity Sibased materials such as rm Si_{1x}Ge_ {x} and deltadoped Si. These materials have brought improvements in device speeds and current drives with the added advantage of monolithic integration into Si VLSI circuits. The bulk of research in Sibased materials has been devoted to the implementation of strained rm Si_{1x}Ge_{x} as the base layer of a rm Si_ {1x}Ge_{x}/Si heterojunction bipolar transistor (HBT). Because of the valence band offset, the rm Si_{1x}Ge _{x} layer can be heavily doped, leading to lower base sheet resistances and hence, improved speed performances. The Ge content in the base can also be graded to increase the drift field in the base. However, very few hole mobility measurements have been done in these strained layers, leading to limitations in device modeling and in understanding the transport behavior in this important material. In addition to rm Si_{1 x}Ge_{x}, much potential also exists in using deltadoping in Si for improved conductivities over those of bulk Si. However, as of yet, deltadoped Si has received little attention. Therefore, this dissertation is dedicated to the investigation of both of these Sibased materials (strained rm Si_{1x}Ge_{x } and deltadoped Si and rm Si_{1x}Ge_ {x}) for the purpose of obtaining higher conductivities than comparably doped bulk Si. This work is divided into three parts to accomplish this objective. The first part is contained in Chapter 3 and is comprised of a comprehensive characterization of the hole mobility in compressively strained rm Si_{1 x}Ge_{x}. Few results have been obtained prior to this research which has led to many inaccuracies in device modeling. The second part of this dissertation in Chapters 4 and 5 is devoted to the study of the mobility behavior in both boron and antimony deltadoped Si and rm Si_ {1x}Ge_{x}. The important discovery of mobility and conductivity enhancement in coupled deltadoped layers is highlighted in Chapter 5. Finally, the third part of this work discusses the implementation of boron delta doped layers in Si homojunction bipolar transistors and FETs. Chapter 6 includes the fabrication of the first coupled deltadoped base layer Si BJT, the first ptype Si deltadoped layer MESFET, the first coupled delta doped layer FET, and the first SiGe delta FET.
 Publication:

Ph.D. Thesis
 Pub Date:
 1994
 Bibcode:
 1994PhDT........71C
 Keywords:

 SILICONGERMANIUM;
 Engineering: Electronics and Electrical; Physics: Condensed Matter