We present a detailed study on the optical properties of GaAsBi/GaAs multiple quantum well structure, optimized for the active area for vertical-external-cavity surface-emitting lasers. The quantum structure was grown by molecular beam epitaxy with every other barrier made thinner to have a homogeneous structure with high photoluminescence (PL) intensity. PL measurements were carried out in a wide temperature range from 4 to 300 K. The PL band of 1.085 eV was attributed to the optical transition in QWs with 8.0%Bi. The S-shaped temperature dependence of PL peak positions showed high localization effect of 30 meV. The internal quantum efficiency (IQE) was evaluated for the bismide structures with a modified ABB* method, which includes contribution from trap-assisted Auger recombination. The calculations showed low IQE of <0.025% for GaAs0.92Bi0.08/GaAs 12 QWs structure, which was explained by the low growth temperature, resulting in a high density of point defects in the material.

We explore quantum well laser diodes for applications in pulse oximetry based on two material systems, namely, classical AlGaAs and a rather exotic GaAsBi, with lasing at around 800 nm and 1100 nm, respectively. These spectral regions and material families were selected due to their closely matched effective penetration depths into soft tissue. An improved design of the band structure of device active areas was tested on both material systems, yielding enhancement of the two main parameters, namely, output power and threshold current. A maximum emission power of the AlGaAs laser diode was registered at 4.9 mW (I = 60 mA, λ = 801 nm). For the GaAsBi-based devices, the target emission of 1106 nm was measured in pulsed mode with a peak output power of 9.4 mW (I = 3 A). The most optimized structure was based on three GaAsBi quantum wells surrounded by parabolically graded AlGaAs barriers. This structure was capable of 130 mW peak power (I = 2 A, λ = 1025 nm) along with a more than tenfold decrease in threshold current to 250 mA compared to a classical rectangular quantum well active region.

We explore quantum well laser diodes based on two material systems, classical AlGaAs, and a rather exotic GaAsBi, with lasing at around 800 nm and 1100 nm, respectively for applications in pulse oximetry. These spectral regions and material families were selected due to closely matched effective penetration depth into soft tissue. An improved design of the band structure of device active areas was tested on both material systems, yielding enhancement of the two main parameters, output power and threshold current. A maximum emission power of the AlGaAs laser diode was registered at 4.9 mW (I = 60 mA, λ = 801 nm). For the GaAsBi-based devices, the target emission of 1106 nm was measured at pulsed mode with a peak output power of 9.4 mW (I = 3 A). While the most optimized structure based on three GaAsBi quantum wells surrounded by parabolically graded AlGaAs barriers was capable of 130 mW of peak power (I = 2 A, λ = 1025 nm) and a more than tenfold decrease in threshold current to 250 mA, when compared to a classical rectangular quantum well active region.

The growth of GaAsBi remains constrained by a narrow and highly sensitive parameter space, limiting its reproducibility and device applicability. In this work, we systematically investigate the growth of GaAsBi layers by extending the explored As/Ga flux range beyond the commonly used near-stoichiometric regime. By combining X-ray diffraction, scanning electron microscopy, atomic force microscopy, and photoluminescence analysis, four distinct growth windows are identified within a beam equivalent pressure As/Ga range of 1 to 8, corresponding to flux ratios of approximately 0.25 to 2. Two of these windows exhibit optical performance suitable for applications in emitters. The near-stoichiometric window (beam equivalent pressure As/Ga ∼4.5) enables the growth of nominal-thickness layers with homogeneous composition, smooth morphology, corresponding to near-balanced growth conditions. In contrast, the previously underexplored window, located at low beam equivalent pressure As/Ga (∼1–2), shows high emission intensity, and enhanced optical properties, narrower spectral shape and lower intensity quenching with temperature despite reduced thickness. Intermediate conditions result in reduced optical quality, while overly As rich conditions suppress Bi incorporation, yielding GaAs-like material. These findings demonstrate that the GaAsBi growth landscape is broader than commonly assumed and provide new pathways for optimizing growth conditions for optoelectronic applications.