Spectral response of InGaAs photocathodes with different emission layers

Area of Science:

• Materials Science
• Semiconductor Physics
• Photocathode Technology

Background:

• Indium Gallium Arsenide (InGaAs) photocathodes are vital optoelectronic components.
• Optimizing their performance requires understanding the trade-offs between emission layer properties and quantum efficiency.

Purpose of the Study:

• To investigate the impact of emission layer composition and thickness on InGaAs photocathode performance.
• To derive a quantum efficiency formula for multi-sublayer InGaAs photocathodes.
• To explore methods for enhancing photocathode performance, specifically electron escape probability and threshold wavelength.

Main Methods:

• Preparation of three InGaAs photocathode samples with varying emission layers using metal organic chemical vapor deposition (MOCVD).
• Activation of photocathodes using Cesium (Cs) and Oxygen (O).
• Measurement of spectral responsivity curves and fitting of experimental quantum efficiency data.

Main Results:

• Thicker emission layers in InGaAs photocathodes correlate with higher spectral responsivity.
• A lower Indium (In) component shifts the threshold wavelength towards shorter wavelengths.
• Higher In component in InGaAs photocathodes leads to a reduced electron escape probability.

Conclusions:

• Achieving both high electron escape probability and a long threshold wavelength simultaneously in InGaAs photocathodes is difficult.
• Incorporating mini transition layers between sublayers significantly reduces interface recombination velocity and increases critical sublayer thickness.
• Mini transition layers are essential for fabricating high-performance InGaAs photocathodes.