May 2021: Prof. Kapadia is awarded an ONR Young Investigator Award.
September 2020: Debarghya wins an AVS Graduate Research Award.
September 2020: Jun’s Paper “High mobility large area single crystal III–V thin film templates directly grown on amorphous SiO2 on silicon” has been written up in SemiconductorToday.
April 2020: Debarghya Sarkar wins the USC Viterbi Ballhaus Dissertation Award.
April 2020: Prof. Kapadia wins the 2020 AVS Peter Mark Memorial Award.
April 2020: Debarghya Sarkar wins the USC ECE Best Dissertation Award.
April 2020: Nick Mehlman wins the Philip Beigler Memorial Award.
Metal Free Hot Electron Driven Electrode Assisted by Plasma Etched Graphene for Hydrogen Evolution Reaction
Hyun Uk Chae, Ragib Ahsan, Jun Tao, Stephen B. Cronin, and Rehan Kapadia
Advanced Materials Interfaces, 8 (6) 2001706, 2021
Hot electron emission from waveguide integrated lanthanum hexaboride nanoparticles
Fatemeh Rezaeifar, Hyun Uk Chae, Ragib Ahsan, Rehan Kapadia
Applied Physics Letters 118 (7), 071108, 2021
Recently, it has been shown that hot-electron photoemission in waveguide-integrated graphene can occur at peak optical power densities many orders of magnitude lower than multiphoton and strong field emission. In this work, we study how the deposition of low-work function lanthanum hexaboride nanoparticles can alter the behavior of hot-electron emission from graphene and thin gold waveguide-integrated hot electron emitters. This approach is promising, as the graphene enables an electrically conductive platform on which to deposit the nanoparticles, while still enabling interaction between the nanoparticles and incident photons. Despite nonideal coatings of LaB6 nanoparticles on the waveguide integrated graphene and gold, there is a nearly order of magnitude improvement over previous graphene-based hot-electron emitters. This hybrid approach demonstrates how a combination of integrated photonics and low-work function coatings can improve the performance of the emerging class of hot-electron emitters.
Monolithic High-Mobility InAs on Oxide Grown at Low Temperature
Debarghya Sarkar, Jun Tao, Ragib Ahsan, Dingzhu Yang, Thomas Orvis, Sizhe Weng, Frank Greer, Jayakanth Ravichandran, Constantine Sideris, Rehan Kapadia
ACS Applied Electronic Materials 2 (7), 1997-2002, 2020
We demonstrate high electron mobility single-crystal InAs mesas monolithically integrated on amorphous dielectric substrates at a growth temperature of 300 °C. Critically, a room temperature mobility of ∼5800 cm2/(V s) was measured, the highest mobility reported for any thin-film semiconductor material system directly grown on a nonepitaxial substrate. Detailed modeling of the scattering mechanisms in the grown material indicates that the mobility is limited by surface roughness scattering, not the intrinsic material quality. We project that reducing the RMS surface roughness of the InAs from 1.8 to 1 nm would produce materials with room temperature mobilities of >10000 cm2/(V s), and RMS roughness of 0.5 nm would result in mobility of ∼20000 cm2/(V s), essentially identical with epitaxially grown materials. These results pave the way for growth of high-mobility materials directly onto the back end of silicon CMOS wafers and other nonepitaxial substrates such as glass, as well as polymers for flexible electronics.