Evaluation of the two-photon absorption characteristics of GaSb/GaAs quantum rings
Journal of Applied Physics
Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa; Department of Electronic and Electrical Engineering, University College London, London, United Kingdom; Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom
The optical parameters describing the sub-bandgap response of GaSb/GaAs quantum rings solar cells have been obtained from photocurrent measurements using a modulated pseudo-monochromatic light source in combination with a second, continuous photo-filling source. By controlling the charge state of the quantum rings, the photoemission cross-sections describing the two-photon sub-bandgap transitions could be determined independently. Temperature dependent photo-response measurements also revealed that the barrier for thermal hole emission from the quantum rings is significantly below the quantum ring localisation energy. The temperature dependence of the sub-bandgap photo-response of the solar cell is also described in terms of the photo- and thermal-emission characteristics of the quantum rings. © 2014 AIP Publishing LLC.
Energy gap; Solar cells; Two photon processes; Hole emission; Localisation; Optical parameter; Photocurrent measurement; Photoresponses; Temperature dependence; Temperature dependent; Two-photon absorptions; Nanorings
EP/G070334/1, EPSRC, Engineering and Physical Sciences Research Council