Research @ IEBL


Our research involves all aspects of Applied Physics/Electronic Materials and Devices to advance the utility of electronic materials in health sciences and medical devices. Over the years, our group pioneered atomic-scale control and understanding of contacts and interfaces in nanoscale devices and the 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: WWe are deeply interested in understanding the spontaneous and stimulated local potential fluctuations and activity in large networks of neurons in 2D and 3D configurations. We are developing technologies that are 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 in collaboration with Dr. Anne Bang’s group at Sanford Burnham Prebys. Our technology is based on vertical and individual electrically addressable nanowire arrays which enable subthreshold and action potential measurements with sensitivity similar to patch-clamp (~ 100 mV AP swings and SNR of ~ 1700). Our 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)

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, Syd Cash (MGH) and Drs. Bob Carter, David Barba and Daniel Cleary (UCSD). Our systematic studies have laid out the scaling rules for intraoperative and electrophysiological devices and increased the yield and uniformity of these devices, which in turn will lead to optimal results in patient care. We are currently extending the use of the technology for utility in clinical trials to help diagnose and treat 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)

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 [48] and to electrochemical reactions in bandgap engineered devices [50]. 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 [62] and recently further unveiled the atomic scale dynamics of Ni-InGaAs reactions both along the radius of the nanowire cross-section [77] and along the channel directions [78]. 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. Vertical High Power GaN MISFETs co-integrated with Si CMOS:  We developed new approaches for strain engineering to dilate 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 greater than ever 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 [67]. 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)

5. Flexible Electronics:
We have extensive expertise in the development of sensors [1] and electronics on flexible substrates and recently developed processes for the realization of thin Si based solar cells with reliable and reproducible high power conversion efficiency. These devices can be used for health-monitoring and intervention and were validated for capability of operation in the RF domain. The overall system integration is currently under development. (Student: Yun Goo Ro)