Short-period scattering-assisted terahertz quantum cascade lasers operating at high temperatures

Area of Science:

• Solid State Physics
• Quantum Electronics
• Terahertz Technology

Background:

• High operating temperatures are essential for practical terahertz quantum cascade lasers (THz QCLs).
• Scattering-assisted injection schemes can increase THz QCL operating temperatures.
• Implementing this scheme in short-period, two-quantum-well structures faces limitations.

Purpose of the Study:

• To identify fundamental limitations in scattering-assisted injection schemes for short-period THz QCLs.
• To propose a novel design concept to overcome these limitations.
• To predict the performance of the proposed design in a specific material system.

Main Methods:

• Non-equilibrium Green's function (NEGF) calculations were employed.
• Analysis focused on current leakage and parasitic absorption via high-energy states.
• A new design utilizing asymmetric quantum well composition was conceptualized.

Main Results:

• Current leakage and parasitic absorption were identified as key limitations in short-period structures.
• The proposed asymmetric wells design effectively suppresses these parasitic effects.
• A peak gain of 40 cm⁻¹ at 230 K is predicted for a 3.5 THz device.

Conclusions:

• Asymmetric quantum well design is a viable strategy to enhance high-temperature performance of THz QCLs.
• The proposed design overcomes fundamental limitations of scattering-assisted injection in short-period structures.
• This advancement paves the way for practical applications of THz QCLs at elevated temperatures.