Date: Thursday, Apr 21st
Presenter: Douglas Tweet, Sharp Laboratories of America
GaN-based semiconductor films have found broad application in light-emitting diodes and also have great potential for high power and high frequency electronic devices. The most widely used substrates are sapphire and SiC, both of which are expensive and of limited size. Consequently, the growth of GaN on silicon substrates has attracted considerable attention. However, there are significant issues with mismatches in thermal expansion and lattice constant, resulting in cracks and high defect densities. I will describe the development of a stress-compensating multilayer buffer which allows the fabrication of thick, low-defect GaN films on silicon substrates. High resolution x-ray diffraction was a primary analysis tool used to optimize the buffer layer.
Doug Tweet is a Principal Research Scientist at Sharp Labs of America in Camas, Washington, where he has been since 1997. He has worked on SiGe and strained Si transistors, Ge IR sensors, development of thin films on silicon (e.g. silicides, high-k and low-k dielectrics), and epitaxial growth of GaN on silicon. More recently he has been investigating novel visible, IR, and x-ray image sensors. Prior to 1997 he spent more than 6 years in Japan with both government (AIST) and industrial (NEC) laboratories mostly in x-ray diffraction analysis of various epitaxial films. He obtained his Ph.D. in Physics in 1990 from the University of Washington. He has about 70 technical publications, and has been granted 70 US patents.