Effective dark current suppression with asymmetric MSM photodetectors in Group IV semiconductors

We have demonstrated for the first time, with both simulations and experiments, the application of an asymmetric metal electrode scheme in Group IV metal-semiconductor-metal photodetectors (MSM-PDs) to effectively lower dark current (I-dark) without sacrificing the photocurrent (I-photo) substantially. A new metric was introduced by normalizing the photocurrent-to-dark current ratio to the input optical power (NPDR) to provide an objective assessment of the detector performance. Improvement of at least 1.4 times in NPDR was obtained with asymmetric MSM-PDs. Finally, the impact of MSM sizing on NPDR was also addressed.