Abstract

III-Nitride semiconductors are of great interest to industry and military due to their optoelectronic and mechanical properties, permitting the development of devices operating in the blue and ultraviolet region of the spectrum and at high temperatures. The main obstacle in obtaining device grade material is crystal quality. This is due to poorly lattice matched substrates as well as what is thought to be incomplete nitrogen incorporation. The first problem is tackled by using better matched substrates or growing buffer layers. Nitrogen incorporation is improved by various methods mostly involving exited gas sources. This dossier covers the growth of III-Nitride semiconductors by using supersonic jets as well as a leak valve, with most work being done to date using NH3, as well as in situ growth monitoring using RHEED.

Chapters 1 through 4 contain my personal biography, degree program, transcript, and a list of other scholarly activity, as required for the dossier by the Department of Materials Science.

Chapter 5 contains an introduction and review on III-Nitride semiconductors, their applications, as well as growth methods commonly used.

Chapter 6 contains a summary of supersonic jet theory and design equations used for the development of jets in our group, with more detailed information to be found in the appendix.

Chapter 7 covers the development of jet sources in our group and their characterization, as well as sections comparing a jet to a leak valve, NH3 dissociation, and the possibility of using RF plasma heating. Also, a new jet design will be suggested to eliminate problems with the current designs.

Chapter 8 discusses the MBE system modifications which had to be performed to make our traditional MBE system compatible with III-Nitride growth, especially for using aggressive NH3 as the N source. Substrates and substrate preparation will also be covered.

RHEED images taken during growth on different substrates will be presented in Chaper 9, as well as reconstructions observed.

A novel technique for GaN growth monitoring using RHEED has been developed and will be presented in Chapter 10. This technique permits substrate temperature calibrations as well as the determination of growth conditions. A suggested growth rate model will be presented and compared to preliminary experimental results obtained. Also, sections on GaN decomposition, growth hysteresis, effects of RHEED on growth rates, and the search for RHEED oscillations are included in the this chapter.

Chapter 11 covers post growth characterization methods used and planned. Emphasis is placed on AUGER and RBS since AUGER is available in our MBE system and RBS is planned to be used more intensively in the future.

Finally, Chapter 12 discusses some of the conclusions drawn so far and future activities planned in the further investigation of III-Nitride semiconductor growth.

Table of Contents