Growth of InAs Quantum Dots in a Metamorphic InGaAs Bottom Cell of an Inverse Metamorphic Solar Cell

摘要

State-of-the-art triple junction inverse metamorphic solar cells have been known to have bottom InGaAs junction that are limiting to the overall radiation performance. It has been proposed that the addition of quantum dots to the bottom junction would improve radiation tolerance of the bottom cell, and thus enhance the triple junctions overall performance in high dose applications. A significant amount of development has been made on quantum dots in metamorphic InGaAs for laser applications, however to date little work has been accomplished for photovoltaic devices. For this study we evaluate the growth of InAs quantum dots on In_(0.31)GaAs grown metamorphically on GaAs. Simulations show that the addition of 50 layers of quantum dots to the bottom junction increases the expected efficiency by 0.2% at a dose of 1x10~(12) protons/cm~2, however this would be a larger increase at a higher dose or if the bottom cell were current limiting. Evaluating the formation by atomic force microscopy with a height of 2.5 nm and density of approximately 7.8x10~(10) dots/cm~2. Temperature dependent photoluminescence measurements were completed to extract an activation energy of 84.6 meV, which corresponds with the calculated electron confinement in the quantum dot.