MOVPE Growth of LWIR AlInAs/GaInAs/InP Quantum Cascade Lasers: Impact of Growth and Material Quality on Laser Performance

The quality of epitaxial layers in quantum cascade lasers (QCLs) has a primary impact on QCL operation, and establishing correlations between epitaxial growth and materials properties is of critical importance for continuing improvements in QCL performance.

Massachusetts Institute of Technology, Lexington, Massachusetts

Quantum cascade lasers (QCLs) are compact coherent optical sources that emit over a wide wavelength range in the mid- to long-infrared (3-25 μm) as well as into part of the terahertz spectrum. With recent developments of AlInAs/GaInAs/InP QCLs exhibiting watt-class output power levels at room temperature in the mid-wave infrared (MWIR, 3-7 μm) and long-wave infrared (LWIR, 8-12 μm) regions, QCLs have become increasingly attractive for numerous technological applications including infrared countermeasures, free-space communications, and chemical and biological sensing.

As interest in QCLs continues to grow, so does the desire to improve performance and understand factors that may ultimately limit these unique and complex devices. QCLs are unipolar devices based on tunneling and intersubband transitions between quantum-confined energy states in the conduction band of a coupled quantum-well structure. These structures are designed using band structure engineering to optimize optical transitions and electron transport for laser characteristics such as wavelength, threshold, power, efficiency, and high-temperature operation.