Imaging Photocarrier Dynamics in Schottky Junction Interface by Scanning Ultrafast Electron Microscopy

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Carrier dynamics at Schottky junction interfaces are critical for efficient photovoltaic, optoelectronic, and photoelectrochemical devices.
• Directly observing carrier behavior within the 2D interfacial plane of these junctions presents significant challenges.

Purpose of the Study:

• To directly image and analyze the spatiotemporal photocarrier dynamics at the n-type gallium arsenide (n-GaAs)/aluminum (Al) Schottky interface.
• To understand the role of interface states in carrier transport and trapping mechanisms.

Main Methods:

• Utilized scanning ultrafast electron microscopy (SUEM) to achieve nanoscale imaging of carrier dynamics.
• Employed numerical simulations with a developed subdiffusion dynamical model to interpret experimental observations.

Main Results:

• Direct visualization of electron-hole separation driven by the built-in electric field at the n-GaAs/Al interface.
• Observation of holes being trapped by interface states and exhibiting quasi-2D subdiffusion along the junction.
• Numerical simulations successfully replicated the observed subdiffusion behavior.

Conclusions:

• The study provides direct insights into carrier transport dynamics within Schottky junctions.
• Interface states play a pivotal role in trapping carriers and influencing their transport behavior.
• Findings contribute to optimizing the performance of semiconductor devices relying on Schottky interfaces.