High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Quantum Cascade Lasers

Background:

• Terahertz (THz) quantum cascade lasers (QCLs) are crucial for various applications.
• InGaAs/InAlAs heterostructures offer potential for high-performance THz QCLs.
• Reproducibility and performance optimization are key challenges in THz QCL development.

Purpose of the Study:

• To investigate and optimize high-power THz QCLs using InGaAs/InAlAs heterostructures.
• To understand the impact of growth-related asymmetries on device performance.
• To achieve high output power and operating temperatures in THz QCLs.

Main Methods:

• Fabrication of InGaAs/InAlAs semiconductor heterostructures with a focus on minimizing growth-related asymmetries.
• Design and optimization of a three-well optical phonon depletion scheme for preferential electron transport.
• Characterization of device performance, including output power and operating temperature, at varying sheet doping densities.
• Utilizing a hyperhemispherical GaAs lens to enhance output power.

Main Results:

• A trade-off exists between maximum operating temperature and output power, influenced by sheet doping density.
• A maximum operating temperature of 155 K was achieved with a moderate doping density (2 × 10^10 cm^-2).
• A peak output power of 151 mW was obtained with a higher doping density (7.3 × 10^10 cm^-2).
• A record output power of 587 mW was achieved for double-metal waveguide structures by attaching a GaAs lens.

Conclusions:

• The study demonstrates the potential of InGaAs/InAlAs heterostructures for high-power THz QCLs.
• Optimization of doping density and waveguide design is critical for balancing performance metrics.
• The achieved record output power highlights the viability of these devices for advanced THz applications.