Photomultiplier (pmt), inspection systems using image sensors, and the pmt or image sensor

Photomultiplier tube comprising a semiconductor photocathode and the photodiode. In particular, the photodiode is a semiconductor layer doped with p- type, the p- type formed on the first surface of the doped semiconductor layer is doped n- type to form a diode on the semiconductor layer and , and a pure boron layer formed on the second surface of the semiconductor layer doped to the p- type. The gap between the semiconductor photocathode and the photodiode is either less than about 1 mm, or less than about 500 [mu] m. Semiconductor photocathode includes gallium nitride, for example, one or more of p- type in doped gallium nitride layer. In other embodiments, semiconductor photocathode may comprise silicon. The semiconductor photocathode may further include a pure boron coating on at least one surface.