Investigation of electrically active defects in InGaAs quantum wire intermediate-band solar cells using deep-level...

Area of Science:

• Semiconductor Nanostructures
• Photovoltaic Devices
• Materials Science

Background:

• Intermediate-band solar cells (IBSCs) offer a pathway to overcome the Shockley-Queisser limit.
• Indium Gallium Arsenide (InGaAs) quantum wires (QWr) are promising nanostructures for IBSCs.
• Understanding charge carrier dynamics and defect states is crucial for optimizing IBSC performance.

Purpose of the Study:

• To investigate the electrical and interface properties of InGaAs quantum wire-based solar cells.
• To identify and characterize defect states influencing device performance across a wide temperature range.
• To correlate trap properties with solar conversion efficiency and external quantum efficiency.

Main Methods:

• Fabrication of InGaAs QWr nanostructures using molecular beam epitaxy.
• Electrical characterization via current-voltage (I-V) and capacitance-voltage (C-V) measurements from 20-340 K.
• Defect analysis using deep-level transient spectroscopy (DLTS).

Main Results:

• Electrical properties of the solar cells varied significantly with temperature.
• DLTS revealed trap states in QWr-doped devices, attributed to the silicon delta-doping layer.
• Identified traps (E1_{QWR_D}, E2_{QWR_D}, E3_{QWR_D}) with activation energies of 0.0037, 0.0053, and 0.041 eV, respectively.
• These traps correlate with decreased solar conversion efficiency and external quantum efficiency at low temperatures.

Conclusions:

• The silicon delta-doping layer is a significant source of traps in InGaAs QWr solar cells.
• These traps detrimentally impact device performance, particularly at lower operating temperatures.
• Further research should focus on mitigating these trap-related losses to enhance solar cell efficiency.