Recombination Dynamics of High-Density Photocarriers in Type-II Ge/Si Quantum Dots

The optical properties and dynamics of charge carriers under high-density photoexcitation in type-II Ge/Si quantum dots (QDs) are studied by time-resolved photoluminescence (PL) measurements at low temperatures. Under high-density photoexcitation, the PL spectra showed a broad band with an extended, high-energy tail, representing a hot-carrier distribution over high-energy states. PL decay measurements revealed that a fast-decay component appeared under high-density photoexcitation, indicating that Auger recombination results in hot-carrier generation in Ge/Si QDs. Moreover, by comparing with thermally annealed Ge/Si QDs, we found that the Auger recombination rate is affected by Ge–Si intermixing at the Ge/Si interface.