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Start of funding 01.07.2010

Attosecond lightwave control of collective electronic motion in nanoscaled metal/III-V semiconductor heterostructures with ultrashort phase-sable laser pulses

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Recent technological developments in the field of ultrafast lasers enabled the generation of intense, phase-controlled few-cycle pulses in the near-infrared (NIR) that can produce ultraviolet (UV) pulses with durations of the order of a few femtoseconds by means of third-harmonic generation in rare gases. Here we aim at exploiting these few-cycle optical fields to generate and control the motion of charge carriers in nanoscaled AlGaN/GaN heterostructures, where a few-femtosecond UV pulse is intended to populate the semiconductor conduction band via a one-photon absorption process, and a synchronized CEP-stable few-cycle NIR laser will serve as the driving electric field imprinting a net momentum change to the generated carriers. Such achievements would represent the realization of ultrafast lightwave electronics.

Final report:
The aim of this project was the development of nanoscaled metal/III-V semiconductor heterostructures at the Molecular Foundry of the Lawrence Berkeley National Lab in Berkeley, California. A nanofabrication process has been developed that includes electron-beam lithography and reactive-ion etching of a gallium nitride (GaN) substrate. In a second step, pairs of gold (Au) electrodes were deposited by electron beam physical vapor deposition on top of the etched GaN surface. Here, a minimal distance of about 50 nm between the individual electrodes was achieved.

These heterostructures were used for experiments of ultrafast light-field control of electronic motion in the semiconductor device that were performed in the group of R. Kienberger at the Max Planck Institute of Quantum Optics in Garching, Germany. Light-phase dependent currents were generated and detected inside the Au/GaN-device by applying strong, phase-stabilized, linearly polarized few-cycle near-infrared light fields at normal incidence to the GaN surface with a polarization perpendicular to the nanotrench between the gold electrodes. The dependency of these currents with respect to the phase and intensity of the applied field has been investigated and is being further analyzed and compared with theoretical simulation at the moment.