Nitrides Seminar - Arman Rashidi, Postdoc, UCSB Materials

11/4/2020 10AM via Zoom

Nitrides Seminar

Wednesday, November 4, 2020, 10:00AM

Zoom Meeting ID: 850 1774 8034      Passcode: 904815

Carrier dynamics in micro-LEDs: decoupling multiphysics effects using RF methods

Abstract: III-V light-emitting diodes (LEDs) are gaining new interest because of their application in emerging technologies such as micro-LED displays and visible-light communication (VLC). Micro-LED displays and VLC require III-V LEDs to operate at the opposite ends of the efficiency spectrum where efficiency is lower in both cases. Micro-LEDs in displays are operated at very low current densities where non-radiative surface recombination is dominant, and efficiency is low. On the contrary, VLC requires the LEDs to operate at high current densities to achieve large modulation bandwidths where efficiency is low due to efficiency droop in nitride LEDs (blue and green) and thermal roll-over in phosphide LEDs (red). Studies of carrier dynamics in micro-LEDs are essential to better understand the fundamental efficiency challenges and enable the design of high-performance micro-LEDs for micro-LED display and VLC applications. In this talk, I will present a comprehensive rate equation approach and RF measurement technique to study the efficiency issues in III-V micro-LEDs under electrical injection and design high-performance LEDs for emerging applications. The RF approach enables decoupling multiphysics processes such as recombination dynamics in the active region, carrier injection and transport, and internal heating. Studying these processes as a function of driving conditions gives insight into the efficiency issues. I will present results from micro-LEDs grown on nonpolar and semipolar GaN, nanowire-based micro-LEDs, and InGaN superluminescence diodes.

BIO: BIO: Arman is currently a Postdoctoral Scholar at the Materials Department at UCSB.  Before joining UCSB, he was a Postdoctoral Fellow at the Center for High‐Technology Materials (CHTM) at the University of New Mexico (UNM) where he was studying carrier dynamics in industry-developed micro-LEDs for AR/VR applications. He earned his Ph.D. at UNM in Feezell’s group (2018), focused on nonpolar and semipolar GaN LEDs for visible-light communication and solid-state lighting. His other areas of work at UNM included MOCVD growth, fabrication, and characterization of III‐nitrides devices such as high‐speed micro-LEDs and superluminescent diodes; vertical‐cavity surface‐emitting lasers; and p-n diodes for power electronics. Before coming to the U.S., he earned his B.Sc. and M.Sc. degrees in Electrical Engineering from Shiraz University (Iran), in 2012 and 2014, respectively. 

Arman’s current research interests at UCSB are the MBE growth of the Dirac semimetal Cd3As2 for the development of next-generation THz transistors and their fabrication and characterization. He further plans to study the topological properties of the Cd3As2 thin films and design novel devices based on the versatile properties of Cd3As2. Arman’s other interest in Prof. Stemmer's lab is the superconductivity of SrTiO3 films grown by MBE.