A hybrid photodetector based on a Gen 3 photocathode and electron-bombarded silicon, non-pixilated, position sensitive, Avalanche Photo Diode (APD) is being developed. The device promises gains of over 106 and sub-millimeter spatial resolution. Signals read at the output of the device can be used to build up images, integrated over the time scales relevant to the process being studied. This integration as a post-process allows significant flexibility in investigation at very low light levels. A design and fabrication process is being developed that can be readily adapted for fast-turnaround proof-of-concept prototypes using a variety of solid state detectors. This process approach also facilitates the parallel development of high Quantum Efficiency (QE), low dark count III-V based photocathodes with a broad range of spectral response from UV to NIR. The Imaging Hybrid Avalanche Photo Diode (IHAPD) is targeted to bioluminescence, chemoluminescence and other low light level spectral imaging. A discussion of a reflection mode hybrid APD development is included as well.
Glass microchannel plates (MCPs) have been in use by numerous manufactuers in a variety of electron multiplication applications. Conventional fabrication of MCPs follow the lines of glass drawing and etching technology. Core and clad glass are drawn together, stacked, drawn again, and finally stacked in the desired pattern. The soluble core is removed with wet chemical processing. These techniques are beginning to run into their feasible limits in terms of channel size, open area ratio, uniformity, and material issues. A strong desire exists to fabricate MCPs with accepted lithographic techniques using Si as the base material to improve uniformity and throughput. Open area ratios of as high as 95% have been achieved using lithography. However, attempts to meet other channel plate characteristics met with little success due to thermal runaway or arcing during operation, high voltage is required for electron gain. Processing improvements have lead to the complete oxidation of the Si matrix eliminating the conducting Si in the channel walls of the Si MCPs allowing high voltages to be supported. Complete oxidation of the Si to silica allows processing temperatures high than conventional glass matrices can withstand. This fact allows for high temperature growth of conductive and secondary emissive materials on the channel walls of the structure. Si MCPs with gain have now been fabricated and tested with voltages comparable to conventional glass MCPs. Channel plate characteristics such as operating voltage, strip current, and gain for Si MCPs will be presented and compared to glass MCPs.
In this paper, we discuss the range of applicability of the drift-diffusion and hydrodynamic models as applied to the study of interdigitated metal-semiconductor-metal photodetectors. The hydrodynamic model is an extension of the standard drift-diffusion technique which determines the electon and hole energies in addition to the carrier concentrations and potential. The hydrodynamic method can properly account for energy dependent phenomena such as nonstationary transport phenomena and thermionic emission currents. The key engineering figure of merit, the time response, is calculated and compared using both models for a 1D device design that closely mimics an InGaAs/AlInAs metal-semiconductor-metal device. Structures incorporating heterobarriers and blocking contacts, wherein differences between the energy dependent and independent models are expected to occur, are examined.