We present a comprehensive study of planar $\mathrm{Nb}$-$\mathrm{Al}$-$\mathrm{Nb}$ Josephson junctions with submicrometer dimensions ($L\approx 100$ nm, active area of approximately $5\times {10}^4{\mathrm{nm}}^2$), where the intrinsic superconductivity of the aluminum weak link plays a crucial role in enhancing device performance. Through a combination of theoretical modeling and experimental characterization, we demonstrate that the aluminum interlayer significantly boosts the critical current $I_c\approx 50\text{μ}\mathrm{A}$ and the characteristic voltage $V_c\approx 1$ mV at $T=4$ K, while maintaining the nonhysteretic current-voltage characteristics essential for digital applications. Our microscopic model, based on self-consistent solutions of the Usadel equations, reveals that this enhancement originates from the coexistence of proximity-induced superconductivity and intrinsic pairing in aluminum, which is particularly pronounced at an optimal boundary resistance. Structural analysis confirms epitaxial $\mathrm{Nb}$-$\mathrm{Al}$ interfaces with minimal interdiffusion, enabling reproducible fabrication of these compact junctions. These results establish $\mathrm{Nb}$-$\mathrm{Al}$-$\mathrm{Nb}$ bridges as promising building blocks for high-density superconducting electronics operating at helium temperatures.

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• Critical current
• Grain boundaries
• Proximity effect
• Quantum information with solid state qubits
• Josephson junctions
• Low-temperature superconductors
• Superconducting qubits
• Weak links