Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructures

Optically excited nanoscale ultrasonic transducers.

In order to work at higher ultrasonic frequencies, for instance, to increase the resolution, it is necessary to fabricate smaller and higher frequency transducers. This paper presents an ultrasonic transducer capable of being made at a very small size and operated at GHz frequencies. The transducers are activated and read optically using pulsed lasers and without physical contact between the in...

Relaxation of optically excited carriers in graphene

Band offsets in transition-metal oxide heterostructures

We measured valence band offsets in Ta2O5–WO3, Ta2O5–Nb2O5 and WO3–Nb2O5 heterostructure couples by in situ x-ray photoelectron spectroscopy, immediately following the bi-layer growth in ultra-high vacuum. Conduction band offsets were estimated using the measured valence band offsets in conjunction with the literature values for the respective band gaps. The offsets between Ta2O5 and WO3 and be...

Dephasing of optically induced excitonic coherences in semiconductor heterostructures

Resonant optical excitation of a direct bandgap semiconductor below the band edge induces excitonic coherences. Experiments based on transient four-wave mixing or cw spectral-hole burning provide an excellent approach to eliminate inhomogeneous broadening and enable determination of the time scale and origin of the decay of the optically induced quantum coherence. Such measurements are of inter...

Determination of conduction band offsets in type-II In0.27Ga0.73Sb/InxAl1−xAsySb1−y heterostructures grown by molecular beam epitaxy

Low-temperature photoluminescence PL has been performed on a set of specially designed In0.27Ga0.73Sb/ InxAl1−xAsySb1−y multiple quantum well MQW heterostructures grown by molecular beam epitaxy in order to provide a measure of the conduction band offsets in this material system. These alloys are of interest for the development of high-speed heterojunction bipolar transistors HBTs that show pro...