Research @ IEBL

Our research involves multiple aspects of Applied Physics/Electronic Materials and Devices to advance the utility of electronic materials in information technology, health sciences and medical devices. Over the years, our group pioneered atomic-scale control and understanding of contacts and interfaces in nanoscale devices, the development of processes for their hybrid integration, and the epitaxial growth of material combinations at thicknesses and properties that were not previously attainable due to lattice and thermal mismatches.  

Our ongoing projects include: 

1. Electro-Neural Interfaces for neuronal network mapping at sub-cellular spatial resolution: We are interested in understanding the spontaneous and stimulated local potential fluctuations and activity in large networks of neurons in 2D and 3D configurations. The lab is developing technologies that can be capable of intracellular intervention for long durations of time and at high spatio-temporal resolution for mapping and stimulation of neuronal activity from primary and human induced pluripotent stem cell neurons and cardiomyocytes in collaboration with Dr. Anne Bang’s group at Sanford Burnham Prebys and Prof. Kelly Frazer's laboratory at UC San Diego, respectively. Our technology is based on vertical and individual electrically addressable nanowire arrays and the resultant devices are projected to have the capacity of targeted and programmable drug delivery and are scalable for fab-compatible processing to serve as the next generation drug screening platform for applications in and beyond precision medicine. (Student: Ren Liu, Sang Heon Lee, Dr. Youngbin Tchoe) 

2. Compliant high fidelity cortical implants: We recently optimized fabrication and surface preparation of high-density PEDOT:PSS microarrays on parylene C for successful intraoperative recording of background, pathological, and functional activity from human subjects in collaboration with Profs. Eric Halgren and Vikash Gilja of UC San Diego and Prof. Sydney Cash  of MGH. We pursued systematic electrochemical studies to determine the scaling laws of electrocoricography devices for intraoperative monitoring. We are currently extending the use of the technology based on PEDOT and other novel materials for utility in clinical trials to help in the diagnose and potential treatment of subjects with a variety of neurodegenerative diseases and for applications in closed loop high fidelity neuroprosthetics. We have ongoing institutional, national, and international collaborations for cortical and spinal cord recording and stimulation across a variety of species. (Students: Sang Heon Lee, Mehran Ganji, Lorraine Hossain, Yun Goo Ro, Hongseok Oh) 

3. Structure-Property Correlation in Nanoscale Materials: We seek to probe and control the dynamics of phase transformation in contacts and interfaces for electronic materials at atomic scale resolution and to tailor the resulting electronic or electrochemical behavior of nanoscale materials and devices. To accomplish this, we utilize the Transmission Electron Microscopy (TEM) facilities at the Center for Integrated Nanotechnologies (LANL/Sandia). Our group has recently discovered a number of novel nanoscale behaviors relevant to solid-state reactions at crystalline boundaries and to electrochemical reactions in bandgap engineered devices. We reported a comprehensive study of the kinetics, dynamics, and structural behavior of Ni-InGaAs for FinFET geometries, resulting strains and anticipated influence on the energy band-edge structure and recently further unveiled the atomic scale dynamics of Ni-InGaAs reactions both along the radius of the nanowire cross-section and along the channel directions. By controlling the kinetics and interfaces of the alloy reactions between Ni and Ge/Si nano-channels, we achieved ultra-short channels with lengths as small as 2.7 nm. Our unique heterogeneous integration scheme allows us to study metal-semiconductor interactions and other solid-state or electrochemical reactions for a wide variety of geometries. The powerful basic science devices and platforms that we are developing are key for enabling future technologies in energy efficient electronics, energy harvesting and storage. (Student: Renjie Chen) 

4. GaN MISFETs co-integrated with Si CMOS:  We developed new approaches for strain engineering to dilate and deflect stresses due to thermal mismatches that resulted in record breaking GaN on Si technology including (1) Over 19 micron thick crack-free GaN on Si, 4-5 times thicker than what has been achieved before, (2) threading dislocation densities of 107 /cm2, which is about two orders of magnitude lower than that previously achieved on Si, and (3) the first vertical GaN MISFETs on Si with performance similar to that of GaN-on-GaN devices. The work builds on our understanding of selective area growth (SAG) in a variety of material systems (As/P/N III-Vs and Ge/Si) which was applied recently for better light extraction from GaN LEDs. We are utilizing other novel growth geometries for high power switches that are co-integrated with Si CMOS drive circuits. (Students: Atsunori Tanaka and Woojin Choi)