Surface photovoltage studies of multilayered structures

Surface photovoltage (SPV) measurements were used to study InAs/GaAs multilayered structures. Two types of sample grown by molecular beam epitaxy were investigated: a quantum dot sample containing a fifteen-layer stack of InAs quantum dots (QD), each separated by GaAs layers, and a multi-quantum well sample. SPV spectra revealed two well-defined transitions and a broad peak. These features were associated with phenomena occurring in the InAs wetting layer-based quantum wells, the InAs-based QDs, and carrier transport within the GaAs buffer layer. A fitting of the Aspnes line shape function to the first derivative of the SPV curves was used to determine the energy and broadening parameter of each transition. Temperature-dependent SPV measurements also revealed that the activation mechanism for the low energy peak was due to carrier emission over the quantum well hetero-barrier. In summary, SPV was shown to be a powerful technique for studying carrier generation and recombination, as well as transport in low dimensional structures.