Schematic structure of InGaAs/GaNAs strain-compensated QDSC fabricated on GaAs (311)B substrate.
AFM images for the topmost surface for 10 layer-stacked layers of strain-compensated InGaAs/GaNAs QDs on GaAs (311)B grown at (a) 480 °C, and (b) 460 °C, respectively. The inset shows the 2D-FFT image.
PL spectra measured at 11 K for 10 layer-stacked InGaAs/GaNAs QDs grown at (a) 480 °C, and (b) 460 °C, respectively. The excitation power is varied from 0.05 to 1.00 W/cm2.
EQE spectra measured for 10 layer-stacked strain compensated InGaAs/GaNAs QDSC on GaAs(311)B, and GaAs p-i-n control cell on GaAs (311)B.
Difference in EQE values, ΔEQE, with (EQEIR_on) and without (EQEIR_off) IR light illumination. Dashed line is guide to the eye, and the measurement details are given in Ref. 11.
Models for 2-step optical transitions observed in InGaAs/GaNAs QDSCs. (a) Electrons are directly pumped from the VB to CB in GaAs by absorption of monochromatic photons (λ < ∼800 nm). The carriers rapidly captured into QDs after thermalization, and then re-pumped from IB to CB by absorption of IR photons. (b) Electrons are pumped from VB to IB due to monochromatic photons (λ > ∼950 nm), and a consequent increase in the population in IB in turn increases optical transitions from IB to CB.
QD parameters measured for 10 layer-stacked layers of strain-compensated InGaAs/GaNAs QDs on GaAs (311)B grown at 480 °C and 460 °C, respectively.
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