The Semiconductor Physics Section conducts a broad range of research supporting advanced electronics for the Navy and the DoD. This research is focused into several areas, including wide band gap materials for high frequency, high power applications, quantum dots for implementations for quantum information, MBE growth and fabrication of semiconductor nanostructures, and theory, particularly of semiconductor nanostructures. For more information, send email to the section head.

Current Areas of Research

Wide Bandgap Materials

Wide bandgap semiconductors are of particular interest to the Navy because of their capability of operating at high power, high temperature and/or high frequency levels that far exceed the capabilities of Si-based technology. The development of high-voltage switching devices employing SiC is actively being pursued, while III-Nitride materials enable the fabrication of high-frequency, high output power microwave devices. Currently, the ability to integrate such devices into Navy systems is limited by device degradation due to material defects. Research is directed toward characterizing both point and extended defects in these systems, identifying those defects that limit device performance and understanding the microscopic mechanisms that lead to device degradation.

Spintronics

Spin-electronics ("spintronics") research is accelerating the development of quantum computing, quantum cryptography, molecular electronics and sensors. While existing semiconductor devices operate in the diffusive transport regime where scattering results in heat dissipation and limits frequency response, spin transport in the ballistic regime offers opportunities which are as yet unexplored and unexploited.

Theory of Nanostructures

Theoretical studies of the unique electronic and optical properties of nanostructures are being done, often in conjunction with experiment in the Branch. A range of techniques are used including many-body approaches for optical properties, ab initio electronic calculations for electronic properties and geometries, finite element techniques for complex geometries, and dynamical matrices for vibrational properties. Recent work has addressed the optical properties of single and coupled quantum dots for implementations for quantum information, quantum gates for quantum information, quantum dots in semiconductor microcavities for advanced quantum electronics, adsorption of a range of adsorbates on carbon nanotubes and it effects on conductance and capacitance for sensors.

Quantum Dots

We have an extensive research effort to explore and develop quantum dot materials for quantum information science and technology. This program encompasses MBE growth, fabrication, optical spectroscopy, and coherent optical control. The materials are based on self-assembled InAs quantum dots on GaAs.

Quantum Dots: Ultrafast Control

As part of an effort to develop solid state implementations for quantum information, ultrafast optical pulse techniques are being used to coherently control the quantum state of electron spins in InAs quantum dots. Optical pulses are used to polarize the spins and to perform operations on the spin states, with the desired operations achieved through pulse detuning from the appropriate resonance(s) and the pulse bandwidth.