Multi-stacked InAs/GaAs quantum dot structures and their photovoltaic characteristics

Multi-stacked InAs/GaAs quantum dot (QD) structures having various number of stacks were grown by molecular beam epitaxy (MBE) on n/sup +/-GaAs substrate. They were fabricated into Schottky barrier devices for photovoltaic characterizations. QDs at a slow growth rate of 0.01 ML/s were chosen for all samples in the whole experiment. Current-voltage (I-V) curves under AM1 solar simulator were measured. It was found that larger number of QD stacks gives more short-circuit current. Contribution to photovoltaic effects by multi-stacked InAs QDs in these matrix materials was confirmed by spectral response measurement, which shows that apart from the sharp drop of photo-response at the band edge of GaAs (/spl sim/0.9 /spl mu/m), spectral peak at 1.1-1.2 /spl mu/m, corresponding to quantized energy of InAs QDs, was observed from these multi-stacked QDs samples. Photocurrent measurement was conducted at 1.1 /spl mu/m wavelength by a band-pass filtered light source to see the correlation between photocurrent at this specific long wavelength and the QD stack numbers.