Image intensifier tube
View Patent ↗An image intensifier tube includes a photocathode ( 20 ) with an active layer ( 52 ) providing an electrical spectral response to photons of light. The photocathode ( 20 ) also includes integral spacer structure ( 42 ) which extends toward and physically touches a microchannel plate ( 22 ) of the image intensifier tube in order to establish and maintain a desirably precise and fine-dimension spacing distance “G” between the photocathode and the microchannel plate. A method of making the photocathode and a method of making the image intensifier tube are described also.
1. A method of making a photocathode, said method comprising steps of:
providing a gallium arsenide (GaAs) temporary substrate;
forming a buffer layer of high-quality single crystalline GaAs on said temporary substrate;
forming a spacer layer of aluminum gallium arsenide (AlGaAs) over said buffer layer;
forming an active layer of GaAs on said spacer layer; and
forming a window layer of AlGaAs on said GaAs active layer to form a photocathode workpiece.
2. The method of claim 1 further including the steps of:
forming a anti-reflective layer of Si 3 N 4 on said window layer; and
forming a thin passivating temporary top layer of SiO 2 over said anti-reflective layer.
3. The method of claim 2 additionally including the step of:
thermal compression bonding said photocathode workpiece to a transparent face plate.
4. The method of claim 3 further including the steps of;
removing said temporary substrate and said buffer layer.
5. The method of claim 4 further including the step of patterning said spacer layer to define an insulative spacer structure extending from said active layer.
6. The method of claim 5 subsequently including the step of decreasing the thickness of the GaAs active layer to a thickness in the rage extending from about 1.2 microns to about 0.45 micron.
7. The method of claim 6 further including the utilization of the reduction in thickness of said active layer to define an active area having an outwardly exposed active surface.
8. The method of claim 7 subsequently including the step of defining an end surface on said insulative spacer structure for contacting engagement with a microchannel plate to establish a spacing dimension between the microchannel plate and the surface of the active area of the active layer of the photocathode.