Modelling of AlAs/GaAs interfacial structures using high-angle annular dark field (HAADF) image simulations

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Heterostructures

Background:

• AlAs/GaAs interfaces are crucial in III-V semiconductor technology.
• Understanding interfacial structure is key to controlling material properties.
• High-angle annular dark-field (HAADF) imaging is a powerful tool for atomic-resolution microscopy.

Purpose of the Study:

• To simulate HAADF images of AlAs/GaAs interfaces with varying structures.
• To investigate the influence of interfacial structure on HAADF image sharpness.
• To compare simulation results with experimental HAADF data.

Main Methods:

• Frozen-phonon multislice simulations of AlAs/GaAs interfacial models (perfect, vicinal/sawtooth, diffusion).
• Calculation of interfacial sharpness as a function of depth for each model.
• Comparison of simulated sharpness with aberration-corrected HAADF experimental data.

Main Results:

• HAADF image sharpness exhibits complex depth-dependent behavior for imperfect interfaces.
• Vicinal structures show probe projection direction significantly impacts measured sharpness.
• Diffusion models (Moison) closely replicate experimental AlAs-on-GaAs interface width trends.
• Linear diffusion models show decreasing interface width with depth, contrasting experimental findings.

Conclusions:

• HAADF imaging analysis of complex interfaces requires careful consideration of structural models.
• Vicinal and diffusion models provide better agreement with experimental data than perfect models for AlAs/GaAs.
• Accurate interpretation of HAADF images depends on the specific interfacial structure and diffusion mechanisms.