Our research encompasses materials science and device physics for discovering, understanding, and tailoring the physical properties of electronic materials at micro, nano, and atomic scales. We are a new experimental group homed by the ECE department at UC San Diego. We currently focus on the following research topics:
1. Overcoming Coherency Limits in Conventional Heteroepitaxy: We are the first to experimentally demonstrate and measure higher critical thicknesses in the heteroepitaxy of lattice mismatched materials on nanowire 'substrates' [44]. Our group's efforts are currently tailored toward the growth of III-V compound semiconductor materials on Si through novel approaches and geometries.
2. Materials for Efficient and Affordable Energy Conversion: We have realized the first epitaxially grown radial Si solar cells with fine control over their doping/absorption profiles in a fab-compatible process [47]. We are currently creating methods for integration of such cells on household and industrial utilities. We are also investing efforts in developing compound semiconductor solar cells on Si substrates through hybrid and monolithic integration schemes.
3. Transistor Channels for Sub-10 nm Technology Node: We have developed techniques that allow realizing sub-10 nm channel lengths in a heterostructured Si/Ge material system and are currently devising processes for sub-10 nm heterostructured III-V channels on Si. We were the first to realize 100% composition modulated Ge-to-Si axial nanowire heterostructures [34] and developed devices that utilized their built-in electric fields for assisting charge carrier transport in their channels [35], and then implemented with collaborators at Brown University tunneling field-effect transistors based on these axial heterostructures [43].
4. In-situ Microscopy of Novel Nanoscale Phenomena: We have recently discovered a number of novel nanoscale phenomena relevant to solid-state reactions at crystalline boundaries[48] and to electrochemical reactions in bandgap engineered devices [49]. We have created platforms that allowed structural-electronic property correlation [21] and contributed to optical-electronic spatio-temporal mapping and their analysis in semiconductor nanostructures [42]. We believe that the powerful basic science tools that we are developing are key for enabling future technologies in energy harvesting and storage, and in low power electronic devices.
5. Bio-Interfaces: We develop technologies that are capable of high-spatial and temporal mapping of neural activity and of simultaneously uncovering details of subcellular processes from a large population of neurons. Our devices are capable of targeted and programmable drug delivery. We address challenges in neuroprosthetics with high density nanoscale probes and microfluidic arrays.