Dynamics and two photon intersubband absorption of photovoltaic quantum structures

Multiple quantum well (InAlAs/InGaAs) based photovoltaic cells and subsystems were grown by molecular beam epitaxy on (001) InP substrates to study the dynamics of the intersubband transitions and the photocurrent behavior with ultrafast and continuous wave (cw) laser spectroscopy, respectively. The surface recombination velocity was determined with photoluminescence and time domain THz spectroscopy by varying the well thickness. Two-photon absorption was observed in a photovoltaic device as an increase in photocurrent from room temperature down to 5 K by illumination of the structures at two different wavelengths.