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Large-area, high-speed vacuum photodiode employing a metal-semiconductor-metal anode
Conference paper

Large-area, high-speed vacuum photodiode employing a metal-semiconductor-metal anode

Tamera A. Yost, Peter R. Herczfeld, Bahram Nabet, Vincent M. Contarino and James A. Culp
Conference proceedings - LEOS (Conference). 1996, v 11, pp 470-471
1997
DOI: https://doi.org/10.1109/CLEO.1997.603455

Abstract

The vacuum photodiode or intensified photodiode (IPD) is used in free-space communication and LIDAR applications where a large area photodetector with low noise, high gain, and a bandwidth of a few gigahertz is needed. The IPD consists of a large area GaAsP photocathode, an electron focusing and accelerating assembly, and a GaAs Schottky barrier or PIN diode as the anode.’ Incident photons strike the surface of the GaAsP photocathode; the emitted beam of electrons is accelerated and focused to a detector by two electrostatic rings. An electron gain of greater than lo3 is achieved via impact ionization of the semiconductor lattice. Currently, the speed of the IPD is limited to 2 Ghz by the 0.3 mm Schottky diode mesa device. To increase the speed of the IPD, the size of the detector must be decreased, which is not possible since the electron beam spot size is fixed at 0.2 mm. Therefore, a new approach is pursued where the mesa structure is replaced by a GaAs interdigital metal-semiconductor-metal (MSM) planar device that maintains the large 0.3 mm area and gain, while providing increased speed.

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