High gain effects for solid-state impact-ionization multipliers

We report the demonstration of a current amplification device, built from silicon and based on impact ionization, which can be cascaded to achieve very high gains. Arbitrary current sources including photodiodes can be interfaced with this device. Testing was done by amplifying the output signal from an independent silicon photodiode. Current gains over 600 were measured for initial photocurrents of 10 nA when two amplifying devices were cascaded together. Additionally, the gain saturation phenomenon of the amplifier due to space-charge effects is investigated. The measured gain saturation is observed to match very well with theoretical predictions. We also present guidelines for obtaining high current gain from the cascaded structure while avoiding gain saturation. Because of the low-noise gain mechanism employed, this device is of potential interest to a variety of fields requiring high-sensitivity optical or electronic detection.