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Open Access Publications from the University of California

Sub Bandgap Light Detection and Photoresponse Amplification in Compensated Silicon P-N Junctions

Abstract

This thesis presents work on two significant research areas in silicon photonics. The first is focused on improving the capability of using single crystal silicon for infrared photon detection. A vertically arrayed core- shell silicon nanowire device has been fabricated and characterized for the investigation of the bias dependence behavior of the sub-bandgap light detection. The intrinsic properties of the nanowire device are based on three physical mechanisms: Franz-Kelydsh effect, quasi-quantum confinement effect, and the impurity state assisted photon absorption. A detailed physical model incorporates all the three physical mechanisms has been developed to analyze its fundamental characteristics and an excellent agreement with the experimental data has been found. The second is on the discovery of a new photoresponse amplification mechanism in highly doped and heavily compensated silicon p-n junctions. The new gain mechanism has been investigated by measuring the photoresponse behavior of a simple planar mesa device. The distinctive characteristics of such an internal amplification mechanism include the gain occurs at bias voltage as low as -2 V and the amplified signal is enhanced rather than suppressed with increasing temperature. A physical model - cycling excitation process (CEP) has been proposed based on the experimental observations. Results from theoretical modeling, fabrication, and experimental measurements of these devices are discussed. In particular, the gain mechanism works in low voltage range and favors room temperature over cryogenic temperature, makes it promising for practical device applications

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