Webinar Series by Leading IEEE Electron Device Luminaries

#Dilute #Nitrides

April 19, 2023 @ 01:00 pm
Bandgap Engineering and Device Applications of Dilute Nitrides
Charles W. Tu
Department of Electrical Engineering, National Chung Hsing University, Taichung, TAIWAN

Incorporating ~1% nitrogen into GaAs, InP, and GaP results in a large bandgap bowing, a large change of conduction band lineup, and in GaP even a large change in the band structure from indirect to direct bandgap. These three bandgap engineering parameters from dilute nitrides are used to improve the performance of electrical, optoelectronic, and photovoltaic devices. (1) When GaInNAs is used as the base of a GaAs heterojunction bipolar transistor (HBT), the turn-on voltage is lowered than that of GaAs-base and GaInAs-base HBT due to the smaller bandgap. (2) Similarly, GaInNAs can be lattice-matched to GaAs and can improve the conversion efficiency of a multijunction solar cell. (3) Incorporating 0.5% of N into GaP results in a direct band gap material. Thus, GaNP solar cells achieve 3 times the conversion efficiency at one quarter of the thickness when compared to GaP solar cells. (4) When InNAsP is the quantum well of an InNAsP/GaInAsP optically pumped quantum-well microcavity laser, the light output is larger than that of GaInAs/GaInAsP counterpart due to the larger conduction-band offset. (5) Similarly, the light output of a GaNP/GaP light-emitting diode (LED) is larger than that of an AlGaInP/GaAs LED at the same wavelength. (6) With the introduction of iPhone X in 2017, which incorporates several vertical-cavity surface-emitting lasers (VCSELs) for facial recognition, long-wavelength (1550 nm) VCSELs have aroused a new interest in dilute nitride GaInNAsSb sandwiched between top and bottom GaAs/AlAs Distributed Bragg Reflectors (DBRs) for eye-safety and cost reasons. 

Charles Tu is a Yushan (Monte Jade) Fellow and Research Professor in the Department of Electrical Engineering, National Chung Hsing University in Taichung, Taiwan, and he is also a Distinguished Professor Emeritus in the Department of Electrical and Computer Engineering (ECE) at University of California, San Diego. He was in the UCSD faculty from 1988 to 2018, was the ECE Department Chair from 1999 to 2003, and was an Associate Dean of the Jacobs School of Engineering from 2004 to 2013. Tu's research interests include novel compound semiconductor heterostructures and nanostructures for electronic, optoelectronic and photovoltaic applications. He was a Distinguished Member of Technical Staff at AT&T Bell Laboratories, Murray Hill, New Jersey from 1980 to 1988. He earned his Ph.D. in Engineering and Applied Science from Yale and his B.Sc. (Hon.) in Physics from McGill University in Montreal. Tu is a Fellow of the IEEE, American Physical Society, and AVS Science and Technology Society. He received Taiwan's Pan Wen-Yuan Foundation Outstanding Research Award in 2009, the North American MBE Innovator Award in 2011, an honorary doctorate from Linköping University, Sweden in 2013, and the IEEE Region 6 (Western U.S.) Educator of the Year Award in 2014.

April 19, 2023 @ 01:00 pm
Bandgap Engineering and Device Applications of Dilute Nitrides
Charles W. Tu
Department of Electrical Engineering, National Chung Hsing University, Taichung, TAIWAN