Research Highlights
WORK PERFORMED AT JPL
Atomistic Nanoelectronic Modeling in 3-D - Prototype development of a bottom-up nanoelectronic modeling tool that enables the analysis of the electronic structure in a nano-scale system based on the representation of each individual atom in the structure. This simulator will enable the analysis of the electronic structure and optical response in a variety of different crystal structures and material systems. The first structures that are analyzed are quantum dots. However, general nanoscale electronics problems such as interface roughness, randomized impurities and radiation effects are to be tackled as well. Demonstrated the simulation of a system as large as 32 million atoms. Parallelized the simulator on a Linux-based Beowulf system. Studied effects due to atomic alloy disorder and interface interdiffusion in quantum dots. [J_2001_4, J_2002_1, J_2002_4, I_2000_2 - I_2003_1]. Optimized material parameters (see below) resulted in good experimental agreement for optical transitions in colloidal quantum dots [J_2001_4, J_2002_3].
Parallelization of Mars Imaging Software (MER) - Convert existing serialMars imaging software (e.g. mosaic generation from many images, left/right eye correlation for two images) to efficient parallel code. Hardware: COTS Linux-based pentium III cluster (beowulf) using MPI. Achieved time reductions from original baseline of 90 minutes to 3 minutes (mosaic software) and 90 minutes to 6 minutes (correlator). This order of magnitude speed-up enables fast feedback to mars rover control. [P_2001_2, P_2001_5]
Genetic Algorithm-Based Optimization and Synthesis - Develop an optimization and synthesis tool based on a massively parallel genetic algorithm (GA) and incorporate various high level simulation tools into the tool box.
- Electron device synthesis: solved the reverse resonant tunneling diode design problem - what is the structure that will generate a particular current-voltage characteristic? NEMO + GA [ P_1999_1, P_1999_3].
- Circuit synthesis: what is the circuit configuration on an FPGA to achieve a Gaussian pulse response? SPICE + GA [P_1999_5, P_2000_1].
- Optical filter synthesis: what is the best pattern on a frequency selective surface to achieve optimal transmission and reflection? [P_1999_2, P_1999_4]
- Material Science: what is the best parameterization of a tight banding bandstructure model to achieve the proper representation of basic material properties such as bandgaps and effective masses? NEMO+GA [J_2000_1, J_2000_2, J_2002_1, J_2002_2]
High Performance Computing Extensions to NEMO 1-D - Parallelize existing NEMO 1-D software on various simultaneous levels using MPI. Ported parallel code to SGI and beowulf massively parallel machines. Achieve unprecedented high fidelity resolution of carrier transport through 1-D heterostructures and uncovered quite unintuitive quantum transport phenomena [J_2001_1, J_2002_5, J_2001_3].
Develop Tight-Binding Model Theory - Collaborate with Prof. Tim Boykin on the fundamental understanding of tight binding models and their applications to quantum transport simulations [J_1999_1 - J_2000_2]
Work Performed at Texas Instruments / Raytheon / UT Dallas
Comprehensive Quantum Electron Transport - Principal designer and developer of the NEMO software. NEMO is the world’s first comprehensive 1-D quantum electron transport simulator including effects due to charging, multiple bands and scattering. NEMO has shown predictive capabilities useful for devices design and analysis. The world’s first high-bias quantum mechanical, simulations of scattering enhanced charging and charge self-consistency of holes and electrons [J_1995_1 - J_1998_7, P_1995_4 - P_1998_1] for RTDs were generated.
Work Performed at Purdue and Ruhr University Bochum
High Bias Coulomb Blockade - Initiated analysis of high bias transport in quantum dots. Key investigator of Coulomb blockade at Purdue University [J_1994_3, P_1995_1].
Linear Response of Coupled Quantum Dots - Proposed experiment on conductance spectroscopy in coupled quantum dots and analyzed experimental feasibility [J_1994_1, J_1994_2]. This work is cited over 70 times!
Scattering - Studied the scattering enhanced valley current in RTDs [J_1993_1, J_1993_2].
2-D Linear Response - Analyzed anomalous Quantum Hall Effect in 2-D electron gas syst. [J_1992_1].
Laser Noise Experiments - Implemented high frequency (200MHz) laser amplitude modulation circuitry. Developed laser stability controller (15kHz) using an external resonance cavity. Measured the propagation of laser noise through optical systems. Calculated and measured higher order, non-linear laser noise fluctuations [J_1990_1, J_1991_1].
Thin Film Deposition - Analyzed the experimental feasibility of a novel fast thin film deposition process. Fabricated first clean metallic films (senior project).