In situ passivation of GaAsP nanowires

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Gallium arsenide phosphide (GaAsP) nanowires (NWs) are promising for advanced solar cell applications.
• Optimizing alloy composition and surface properties is crucial for enhancing NW performance in tandem solar cells.
• Surface passivation is key to improving optical properties and carrier dynamics in semiconductor nanowires.

Purpose of the Study:

• To investigate the structural and optical properties of GaAsP nanowires grown by molecular-beam epitaxy.
• To tune the alloy composition for optimal transition energy in tandem III-V/silicon solar cells.
• To explore the effect of in situ Ga(As)P shell passivation on GaAsP NW luminescence and carrier dynamics.

Main Methods:

• Molecular-beam epitaxy (MBE) for GaAsP nanowire growth.
• In situ deposition of radial Ga(As)P shells with varying compositions and thicknesses.
• Optical characterization, including photoluminescence (PL) intensity and time-resolved luminescence decay measurements.

Main Results:

• Adjusting GaAsP alloy composition allowed tuning of the transition energy for tandem solar cell applications.
• An unintentional shell formed during growth, and subsequent in situ GaP shell deposition passivated the NW surface.
• A 5 nm thick GaP shell optimized passivation, enhancing luminescence intensity by two orders of magnitude and extending luminescence decay times (from 4 ps to 85 and 540 ps).

Conclusions:

• Optimal passivation of GaAsP nanowires (1.78 eV band gap) is achieved with a 5 nm GaP shell.
• Surface passivation significantly boosts luminescence intensity and prolongs carrier lifetimes, crucial for efficient solar energy conversion.
• The study demonstrates a viable method for enhancing the performance of GaAsP nanowires for next-generation tandem solar cells.