Structural properties of InGaAs-based strain balanced MQW for photovoltaic applications

A novel system for photovoltaic applications which combines InGaAs based strain-balanced MQW with compositionally graded InGaAs/GaAs virtual substrate was designed and grown to extend the absorption edge to 1 eV. Fully relaxed buffer layers were successfully grown providing the confinement of misfit dislocations at the buffer/substrate interface and a strain-free MQW with low threading dislocation density, less than 10(5) cm(-2). The misfit dislocation network, however, results in marked cross-hatched morphology that was found to affect the lateral strain distribution in the whole structure. Lateral composition fluctuations in the MQW have been discussed in terms of step bunching mechanisms occurring at the valleys of the cross hatched surface.