Camera tube target structure exhibiting greater-than-unity amplification

Claim 2

In a television-camera pick-up tube, a novel target structure which exhibits greater-than-unity amplification (gain), the target structure having one side facing incident scene light and having an opposite side facing a scanning electron beam, the novel target structure comprising, in combination, a glass plate (0) on that side of the target structure exposed to scene light; a transparent signal electrode (1) on the side of the glass plate facing the electron beam; a homogeneous layer (2) of n-type photoconductive semiconductor material on the side of the transparent signal electrode facing the electron beam; a homogeneous layer (4) of n-type semiconductor material on the side of the photoconductive layer facing the beam, and having a resistivity greater than 10 8 ohm-centimeters, the interface (3) between the pair of n-type semiconductor layers being possessed of a multitude of interface states located at energy levels such as to capture both holes optically generated within the n-type photoconductive layer (2) and beam-injected electrons, the interface states being predominently acceptor-level interface states, the edge energy of the valence band of the layer (4) of 10 8 ohm-centimeter material being at the interface lower than the edge energy of the valence band of the n-type photoconductive layer (2) at the interface (3) to create a potential barrier for holes preventing holes optically generated in the n-type photoconductive layer (2) from crossing the interface (3) to the beam-side of the target structure.

Claim 3

In a television-camera pick-up tube, a novel target structure which exhibits greater-than-unity amplification (gain), the target structure having one side facing incident scene light and having an opposite side facing a scanning electron beam, the novel target structure comprising, in combination, a glass plate on that side of the target structure exposed to scene light; a transparent signal electrode on the side of the glass plate facing the electron beam; a pair of layers of material on the side of the transparent signal electrode facing the electron beam, one of the pair of layers being a homogeneous photoconductive semiconductor layer, the other of the pair of layers being a homogeneous layer of non-metallic material having a resistivity greater than 10 8 ohm-centimeters, the interface between the pair of layers being possessed of a multitude of interface states located at energy levels such as to capture both first-polarity charge carriers optically generated within the photoconductive layer and second-polarity charge carriers injected into the target structure from the side of the interface opposite to that at which the photoconductive layer is located, the edge energy of the conduction band of the homogeneous layer at the light-side of the interface being higher than the edge energy of the conduction band of the homogeneous layer at the beam-side of the interface to create a potential barrier for electrons travelling across the interface in the direction from the beam-side to the light-side of the target structure and thereby cause such electrons to become trapped in the interface states, the edge energy of the valence band of the homogeneous layer at the beam-side of the interface being lower than the edge energy of the valence band of the homogeneous layer at the light-side of the interface to create a potential barrier for holes travelling across the interface in the direction from the light-side to the beam-side of the target structure and thereby cause such holes to become trapped in the interface states, the capture in the interface states of the first-polarity charge carriers optically generated in the photoconductive layer lowering the potential barrier for the passage of the injected second-polarity charge carriers through the interface, so that one optically generated first-polarity charge carrier captured in an interface state by reducing the potential barrier for injected second-polarity charge carriers during its interface entrapment allows more than one injected second-polarity charge carrier to cross the interface, thereby creating greater than unity amplification.

Claim 4

In a television-camera pick-up tube, a novel target structure which exhibits greater-than-unity amplification (gain), the target structure having one side facing incident scene light and having an opposite side facing a scanning electron beam, the novel target structure comprising, in combination, a glass plate on that side of the target structure exposed to scene light; a transparent signal electrode on the side of the glass plate facing the electron beam; a pair of layers of material on the side of the transparent signal electrode facing the electron beam, one of the pair of layers being a homogeneous photoconductive semiconductor layer, the other of the pair of layers being a homogeneous layer of non-metallic material having a resistivity greater than 10 8 ohm-centimeters, the interface between the pair of layers being possessed of a multitude of interface states located at energy levels such as to capture both first-polarity charge carriers optically generated within the photoconductive layer and second-polarity charge carriers injected into the target structure from the side of the interface opposite to that at which the photoconductive layer is located, the edge energy of the conduction band of the homogeneous layer at the light-side of the interface being higher than the edge energy of the conduction band of the homogeneous layer at the beam-side of the interface to create a potential barrier for electrons travelling across the interface in the direction from the beam-side to the light-side of the target structure and thereby cause such electrons to become trapped in the interface states, the edge energy of the valence band of the homogeneous layer at the beam-side of the interface being lower than the edge energy of the valence band of the homogeneous layer at the light-side of the interface to create a potential barrier for holes travelling across the interface in the direction from the light-side to the beam-side of the target structure and thereby cause such holes to become trapped in the interface states, the capture in the interface states of the first-polarity charge carriers optically generated in the photoconductive layer lowering the potential barrier for the passage of the injected second-polarity charge carriers through the interface, so that one optically generated first-polarity charge carrier captured in an interface state by reducing the potential barrier for injected second-polarity charge carriers during its interface entrapment allows more than one injected second-polarity charge carrier to cross the interface, thereby creating greater than unity amplification.

Claim 5

In a television-camera pick-up tube, a novel target structure which exhibits greater-than-unity amplification (gain), the target structure having one side facing incident scene light and having an opposite side facing a scanning electron beam, the novel target structure comprising, in combination a glass plate on that side of the target structure exposed to scene light; a transparent signal electrode on the side of the glass plate facing the electron beam; a pair of layers of material on the side of the transparent signal electrode facing the electron beam, one of the pair of layers being a homogeneous photoconductive semiconductor layer, the other of the pair of layers being a homogeneous layer of non-metallic material having a resistivity greater than 10 8 ohm-centimeters, the interface between the pair of layers being possessed of a multitude of interface states located at energy levels such as to capture both first-polarity charge carriers optically generated within the photoconductive layer and second-polarity charge carriers injected into the target structure from the side of the interface opposite to that at which the photoconductive layer is located, the edge energy of the conduction band of the homogeneous layer at the light-side of the interface being higher than the edge energy of the conduction band of the homogeneous layer at the beam-side of the interface to create a potential barrier for electrons travelling across the interface in the direction from the beam-side to the light-side of the target structure and thereby cause such electrons to become trapped in the interface states, the edge energy of the valence band of the homogeneous layer at the beam-side of the interface being lower than the edge energy of the valence band of the homogeneous layer at the light-side of the interface to create a potential barrier for holes travelling across the interface in the direction from the light-side to the beam-side of the target structure and thereby cause such holes to become trapped in the interface states.

Claim 6

In a television-camera pick-up tube, a novel target structure which exhibits greater-than-unity amplification (gain), the target structure having one side facing incident scene light and having an opposite side facing a scanning electron beam, the novel target structure comprising, in combination a glass plate on that side of the target structure exposed to scene light; a transparent signal electrode on the side of the glass plate facing the electron beam; a pair of layers of material on the side of the transparent signal electrode facing the electron beam, one of the pair of layers being a homogeneous photoconductive semiconductor layer, the other of the pair of layers being a homogeneous layer of non-metallic material having a resistivity greater than 10 8 ohm-centimeters, the interface between the pair of layers being possessed of a multitude of interface states located at energy levels such as to capture both first-polarity charge carriers optically generated within the photoconductive layer and second-polarity charge carriers injected into the target structure from the side of the interface opposite to that at which the photoconductive layer is located, the edge energy of the conduction band of the homogeneous layer at the light-side of the interface being higher than the edge energy of the conduction band of the homogeneous layer at the beam-side of the interface to create a potential barrier for electrons travelling across the interface in the direction from the beam-side to the light-side of the target structure and thereby cause such electrons to become trapped in the interface states, the edge energy of the valence band of the homogeneous layer at the beam-side of the interface being lower than the edge energy of the valence band of the homogeneous layer at the light-side of the interface to create a potential barrier for holes travelling across the interface in the direction from the light-side to the beam-side of the target structure and thereby cause such holes to become trapped in the interface states.

Claim 7

In a television pick-up tube as defined in claim 3, the photoconductive layer being located at the light-side of the interface, the non-metallic layer being located at the beam-side of the interface, the first-polarity charge carriers optically generated within the photoconductive layer being optically generated holes, the injected second-polarity charge carriers being electron-beam-injected electrons, the interface states being predominantly acceptor-level interface states.

Claim 8

In a television pick-up tube as defined in claim 4, the non-metallic layer being a layer of semiconductor material.

Claim 9

In a television pick-up tube as defined in claim 5, the two homogeneous layers being layers of semiconductor material of the same conductivity type.

Claim 10

In a television pick-up tube as defined in claim 6, the photoconductive layer being a layer of n-type photoconductive material, the non-metallic layer being a layer of n-type semiconductor material.

Claim 11

In a television pick-up tube as defined in claim 4, the photoconductive layer being a layer of n-type CdSe.

Claim 12

In a television pick-up tube as defined in claim 8, the non-metallic layer being a layer of one of the materials in the group consisting of zinc selenide, zinc sulfide, arsenic sulfide, antimony sulfide, calcium fluoride, magnesium fluoride, and silicon oxide.

Claim 13

In a television pick-up tube as defined in claim 4, the photoconductive layer being a layer of n-type CdSe, the non-metallic layer being a layer of n-type ZnSe.

Claim 14

In a television pick-up tube as defined in claim 9, further including between the layer of n-type CdSe and the transparent signal electrode a layer of material having a large forbidden energy gap for increasing the blue sensitivity of the target structure.

Claim 15

In a television pick-up tube as defined in claim 11, the material having the large forbidden energy gap being zinc selenide.