Modeling with graded interfaces: Tool for understanding and designing record-high power and efficiency mid-infrared...

Area of Science:

• Optoelectronics and Photonics
• Semiconductor Physics
• Quantum Engineering

Background:

• Quantum cascade lasers (QCLs) are crucial for mid-infrared applications.
• Interface roughness (IFR) scattering significantly impacts QCL performance.
• Accurate modeling of IFR is essential for optimizing QCL design.

Purpose of the Study:

• To develop and validate a graded-interfaces model for mid-infrared QCLs.
• To accurately reproduce and understand the electro-optical characteristics of high-performance QCLs.
• To utilize the model for designing next-generation QCLs with improved efficiency.

Main Methods:

• Generalized formalism for interface-roughness (IFR) scattering.
• Modification of the IFR model for mid-infrared emitting quantum cascade lasers (QCLs).
• Atom-probe tomography analysis for IFR parameter extraction.
• Device design and simulation using the graded-interfaces model.

Main Results:

• Accurate reproduction of electro-optical characteristics for published record-performance QCLs.
• Identification of key factors for high performance: direct injection and photon-induced carrier transport.
• Quantification of high normalized leakage current density due to IFR-triggered shunt-type leakage.
• Design of an 8.1 µm-emitting QCL with suppressed carrier leakage and record wall-plug efficiency (22.2%).

Conclusions:

• The graded-interfaces model is a powerful tool for QCL design and optimization.
• Suppressed carrier leakage and optimized injection are critical for high-efficiency QCLs.
• The developed model facilitates the design of QCLs approaching fundamental performance limits.