Nanowire Optoelectronics at Infrared: Modeling, Epitaxy, and Devices

Speaker: Dingkun Ren
Affiliation: Ph.D. Candidate - UCLA

Abstract:  Bottom-up semiconductor nanowires and their arrays have been frequently highlighted as building blocks for next-generation optoelectronic devices. Compared with planar thin films, vertical nanowires have unique properties, namely three-dimensional (3-D) geometries with high surface-to-volume ratios, small junction area, and heteroepitaxy. These capabilities lead to the designs of high-performance, integrated, and compact device platforms. Since the relationship between the 3-D nanowire geometries and the material properties introduces unique aspects of carrier dynamics, studying these dynamics is critical to exploring the rich electrical properties underlying the material characterizations and guiding the design of nanowire optoelectronic devices.

In this study, we provide new insight into nanowire optoelectronics at infrared by investigating nanowire modeling, epitaxy, and devices. First, we combine optical and electrical simulations to develop a more powerful scheme of 3-D modeling, allowing us to comprehensively interpret and understand the temporal and spatial motion of carriers in nanowires. With the new insight as well as nanowire designs obtained from modeling, we then tackle the heteroepitaxy of nanowires on lattice mismatched substrates by selective-area metal-organic chemical vapor deposition and demonstrate the growth of high-quality materials within the 2 – 5 µm wavelength spectrum. Finally, we demonstrate short-wavelength infrared nanowire photodetectors that approach room-temperature photodetection and develop device platforms for mid-wavelength infrared optoelectronics. These three points of focus in this study–modeling, epitaxy, and devices–are closely intertwined, and together provide a holistic picture of 3-D nanowire performance.

We believe the presented theoretical and experimental work will stimulate more validating studies of nanowire optoelectronics at infrared to further reveal the inherent carrier dynamics of nanowires and develop more sophisticated nanowire optoelectronic devices.

Biography:   Dingkun Ren received his M.S. degree in Electrical and Computer Engineering from UCLA in 2013, and B.E. degree in Mechanical Engineering from Tianjin University, China in 2011.  Throughout the PhD career, Dingkun has authored and co-authored 10 publications (including seven first-author papers) and has given seven conference presentations (including three invited talks).  He is currently a member of the Optical Society (OSA), the Materials Research Society (MRS), and SPIE. Dingkun actively serves as a reviewer of various international journals, such as Optics Letters, Optics Express, Scientific Reports, Applied Physics Letters, and Journal of Applied Physics. He is also a teaching fellow of UCLA.

For more information, contact Prof. Diana L. Huffaker (huffaker@ee.ucla.edu)

Date/Time:
Date(s) - Aug 02, 2018
2:30 pm - 4:00 pm

Location:
E-IV Tesla Room #53-125
420 Westwood Plaza - 5th Flr., Los Angeles CA 90095