Extended defects in InGaAs/InGaAs strain-balanced multiple quantum wells for photovoltaic applications

Different strain-balanced InGaAs/InGaAs multiple quantum wells (MQWs) were grown on (001) InP changing the In composition in the wells/barriers in order to extend the absorption edge beyond 2 μm for thermophotovoltaic applications. The strain increase in the structures results in the formation of isolated highly defected regions taking their origin from lateral layer thickness modulations. Experimental results are consistent with the existence of a critical elastic energy density for the development of MQW waviness. An empirical model for predicting the maximum number of layers that can be grown without modulations as a function of the strain energy stored in the MQW period is presented