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This paper details the status of a program at Intevac ATD to develop high sensitivity transmission photocathodes which function in the 0.95 -1 .7 micron wavelength range. The goal of the program is to develop this technology for use with both imaging and non-imaging detectors. Sealed tube results are presented. Measured performance characteristics include: cathode spectral response, dark current, linearity and the effects of cooling. A brief discussion of planned development, potential applications and simple modeling illustrating the advantages of the proposed detectors are included.

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An ultra-low-noise, high-speed, hybrid photomultiplier tube sensitive from 900 to 1300 nm optical wavelengths is described. The device, also known as an intensified photodiode (IPD), uses an active transferred electron (TE) photocathode with the quaternary In :69 Ga :31 As :67 P :33 photo-absorbing layer and a GaAs Schottky avalanche photodiode (SAPD) anode. The detector has a combined electron bombarded and avalanche gain of over 15 000 which is sufficient to overcome preamplifier noise and provide high internal counting efficiency of approximately 85%. At an active cathode bias of 1.5 V the room temperature cathode dark countw rate is 6:67 2 10 5 /s. Cooling reduces this substantially corresponding to a dark current activation energy almost equal to the bandgap of the In:69Ga:31As:67P:33 layer.

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