Silicon-based diodes are fundamental components in modern semiconductor technology. However, their performance is hindered by the Boltzmann switching limit, resulting in an ideality factor larger than 1 and a high operating voltage. In this work, we propose a silicon cold-source diode (CSD) to realize energy-efficient switching with subunity ideality factor. The silicon cold-source diode integrates a $p$-$n$ junction with a cold source comprised of a metal layer sandwiched between $N$-type and $P$-type silicon. Through first-principles transport calculations, it is demonstrated that the silicon cold-source diode can enable low-energy carrier injection and enhanced current by adjusting the doping concentration and varying the metal material. The CSDs can realize a subunity ideality factor, as low as 0.79. The operating voltage can be further reduced to 0.4 V. At the same time, the rectification characteristics can also be improved with the on-off current ratio exceeding ${10}^9$. By optimizing the metal layer, on-state current comparable to $p$-$n$ diode can be achieved in CSDs. We have designed potential preparation processes for CSDs and analyzed the associated challenges. The doping concentration in the $N$-type and $P$-type regions is critical to device performance. Insufficient doping concentration leads to significant performance degradation. These findings serve as a valuable framework for the design and optimization of cold-source diodes compatible with CMOS technology, particularly tailored for low-power applications.

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• Band gap
• Density of states
• Local density of states
• Diodes
• Band structure methods
• Density functional theory
• First-principles calculations