A Structural Study of InGaAs/InGaAs Strain‐Balanced MQW for TPV Applications

Multi‐quantum well photovoltaic cells offer a number of advantages over conventional “single‐gap”cells for thermophotovoltaic applications, first of all because they can reach a higher open circuit voltage under the same radiation source and with the same absorption edge. Material quality issues and the constraints imposed by the commercial available substrates indicate that InxGa1−xAs/InyGa1−yAs/InP strain‐balanced heterostructures are suitable to obtain good quality multi‐quantum wells with an absorption edge just below 2.0 μm. Structural stability in the presence of a high density of elastic energy such as in the case of a strain‐balanced multi‐layer is a very important issue to be addressed by optimising key parameters like composition, thickness of wells and barriers and number of periods. In this paper we present and discuss the mechanisms of plastic relaxation of these structures with a particular attention to the impact of the extended defects generated by the local breakdown of the crystal lattic...