No abstract

The fabrication and characterization of an infrared photodetector based on GaAs droplet epitaxy quantum dots embedded in Al 0.3 Ga 0.7 As barrier is reported. The high control over dot electronic properties and the high achievable number density allowed by droplet epitaxy technique permitted us to realize a device using a single dot layer in the active region. Moreover, thanks to the independent control over dot height and width, we were able to obtain a very sharp absorption peak in the thermal infrared region (3-8 μm). Low temperature photocurrent spectrum was measured by Fourier spectroscopy, showing a narrow peak at 198 meV (∼6.3 μm) with a full width at half maximum of 25 meV. The observed absorption is in agreement with theoretical prediction based on effective mass approximation of the dot electronic transition.

This paper presents an experimental and theoretical study on the impact of doping and recombination mechanisms on quantum dot solar cells based on the InAs/GaAs system. Numerical simulations are built on a hybrid approach that includes the quantum features of the charge transfer processes between the nanostructured material and the bulk host material in a classical transport model of the macroscopic continuum. This allows gaining a detailed understanding of the several physical mechanisms affecting the photovoltaic conversion efficiency and provides a quantitatively accurate picture of real devices at a reasonable computational cost. Experimental results demonstrate that QD doping provides a remarkable increase of the solar cell open-circuit voltage, which is explained by the numerical simulations as the result of reduced recombination loss through quantum dots and defects.

No abstract

We present a numerical study on the influence of wetting layer states and doping on the photovoltage loss of InAs/GaAs quantum dot solar cells. Quantum-mechanical simulations are used to analyze how the reduction of wetting layer by Al(Ga)As overgrowth changes the quantum dot electronic states. Device-level simulations allows to correlate such changes with the achievable open circuit voltage. Almost full open circuit voltage recovery is predicted by combining wetting layer reduction, to realize thermal decoupling of barrier and quantum dot confined states, and doping to suppress radiative recombination through the quantum dot confined states.