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Published on: October 13, 2017
T-shaped GaAs quantum-wire lasers and the exciton Mott transition
1Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan. CREST, JST, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
Summary
High-quality T-shaped gallium arsenide (GaAs) quantum-wire lasers demonstrate electron-hole plasma gain, challenging the role of excitons in the exciton Mott transition. Biexcitons play a key role in this transition in one-dimensional systems.
Area of Science:
- Semiconductor physics
- Quantum optics
- Materials science
Background:
- One-dimensional (1D) systems, such as quantum wires, are crucial for fundamental physics studies.
- Understanding carrier dynamics and gain mechanisms in these systems is key for advanced laser technology.
Purpose of the Study:
- To investigate the laser device physics and many-body physics in clean 1D systems using T-shaped GaAs quantum-wire (T-wire) lasers.
- To determine the origin of laser gain above threshold and study carrier density effects on photoluminescence (PL).
Main Methods:
- Fabrication of T-wire lasers using cleaved-edge overgrowth and molecular beam epitaxy with a growth-interrupt high-temperature anneal.
- Characterization via current-injection and optical pumping experiments.
- Systematic micro-photoluminescence (micro-PL) studies at varying carrier densities.
Main Results:
- Achieved low threshold current (0.27 mA at 30 K) in a T-wire laser with 20 periods and a 0.5 mm cavity.
- Lasing energy observed below the free exciton PL peak, indicating gain from electron-hole (e-h) plasma at high carrier densities.
- Micro-PL showed evolution from exciton to biexciton peaks, then to e-h plasma band, highlighting biexcitons' role in the exciton Mott transition.
Conclusions:
- Laser gain in these T-wire lasers originates from e-h plasma, not free excitons.
- Biexcitons are significant in the exciton Mott transition, but current theories may require refinement.
- The study provides insights into many-body physics in clean 1D semiconductor systems.
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