Influence of barrier material and structure on carrier quantum confinement in GaAsBi quantum wells (QWs) is studied comprehensively. Single- and multi-QW structures were grown using solid-state molecular beam epitaxy with conventional rectangular, step-like and parabolically graded AlGaAs barrier designs. It was discovered that room temperature photoluminescence is increased by more than 50 times in the GaAsBi QWs with parabolically graded barriers (PGBs) if compared to standard rectangular and step-like structures. The enhancement of photoluminescence was reproducible within the range of growth parameters. The carrier localization and increase of trapping efficiency in GaAsBi QWs is responsible for observed enhancement in radiative properties of PGB structures. The random potential field fluctuations for carriers were increased up to 44 meV due to the blurred well-barrier interface causing the conditions for Bi content and/or well width variations. Due to the impact of self-organizing effects on the reproducibility of optical properties, the GaAsBi QWs with AlGaAs PGBs open the window for fabrication of 1.0-1.55 μm wavelength emission lasers based on GaAsBi quantum structures.

Fabry–Perot laser diodes based on (Al, Ga)As and Ga(As, Bi) with single or multiple parabolic or rectangular-shaped quantum wells (QWs) emitting at the 780–1100 nm spectral range were fabricated and investigated for optimization of the laser QW design and composition of QWs. The laser structures were grown using the molecular beam epitaxy (MBE) technique on the n-type GaAs(100) substrate. The photolithography process was performed to fabricate edge-emitting laser bars of 5 μm by 500 μm in size. The temperature-dependent power-current measurements showed that the characteristic threshold current of the fabricated LDs was in the 60–120 mA range. Light and current characteristics were almost linear up to (1.2–2.0) I_th. Low-frequency 10 Hz–20 kHz electrical and optical noise characteristics were measured in the temperature range from 70 K to 290 K and showed that the low-frequency optical and electrical noise spectra are comprised of 1/f and Lorentzian-type components. The positive cross-correlation between optical and electrical fluctuations was observed.

Laser diodes with parabolic and rectangular AlGa(As,Bi)/AlGaAs QWs were grown by MBE on n-GaAs(001). Operating wavelength was controlled by QW width and material composition. Laser bars processed by UV lithography were characterized by electroluminescence and I-V measurements.

In this work we are focusing on the semiconductor lasers based on AIII-B5-Bi, namely bismides, alloy grown by molecular beam epitaxy. Bismide semiconductor laser diodes have a potential to become the foundation of optical systems for automotive applications. Optimization of growth parameters and analysis of obtained results will be presented.

Infraraudoniesiems jutikliams skirtų bismidinių junginių auginimas ir tyrimas