Optimum high gain-bandwidth phototransistor structure

Claim 2

A semiconductor device comprising: a body including a first semiconductor substrate of a first conductivity type and a surface layer of semiconductor material of the same conductivity type disposed on said first semiconduCtor substrate, said surface layer having a resistivity substantially lower than the resistivity of said first semiconductor substrate; a diode in one portion of said body comprising a semiconductive region of a second conductivity type extending from the surface of said body through said surface layer and into said semiconductor substrate, said semiconductive region forming a PN junction with said substrate and layer; and a transistor in another portion of said body comprising a first semiconductive region of said second conductivity type extending from the surface of said body into said surface layer and terminating short of said semiconductor substrate, said first semiconductive region forming a PN junction with said surface layer, and a second semiconductive region of said first conductivity type extending from the surface of said body into said first semiconductive region, said second semiconductive region forming a PN junction with said first semiconductive region.

Claim 3

The device of claim 1 wherein the resistivity of said first semiconductor substrate is the order of 50 to 200 ohm-centimeters and the resistivity of said surface layer is of the order of 1 to 10 ohm-centimeters.

Claim 4

The device of claim 2 wherein the thickness of said surface layer is of the order of 2 to 5 microns and the depth of said semiconductive region of the diode portion is of the order of 5 to 10 microns.

Claim 5

The device of claim 1 wherein said first conductivity type is N type semiconductor material and said second conductivity type is P type semiconductor material.

Claim 6

The device of claim 1 wherein the first semiconductive region in the transistor portion of the body extends into contact with said semiconductive region in said diode portion of the body and provides a base-to-base connection between the diode and the transistor.

Claim 7

The device of claim 1 including an insulation layer extending over the surface of said body, an electrical connection extending over the insulation layer and through the insulation layer into contact with both the first semiconductive region in the transistor portion of the body and the semiconductive region in said diode portion of the body, and additional contact means making electrical connection with additional regions of said device.

Claim 8

The device of claim 1 including a second semiconductor substrate of said first conductivity type below said first semiconductor substrate, said second semiconductor substrate being of substantially lower resistivity than said first semiconductor substrate; a buried layer of said first conductivity type and of substantially lower resistivity than said first semiconductor substrate, said buried layer being in said transistor portion of the body and between said first semiconductor substrate and said surface layer; and a connecting layer of low resistivity material of said first conductivity type coupling said buried layer with said second semiconductor substrate.

Claim 9

The device of claim 6 wherein said connecting layer is located on the surface of a pocket extending from the surface layer of the transistor and down through said buried layer, said first substrate and into said second substrate.

Claim 10

A semiconductor device comprising: a body including a first semiconductor substrate of a first conductivity type and a surface layer of semiconductive type material of the same conductivity type disposed on said first semiconductor substrate, said surface layer having a resistivity substantially lower than the resistivity of said first semiconductor substrate; a first semiconductive region of a second conductivity type and extending from the surface of the body through said surface layer and into said first semiconductor substrate, said first semiconductive region and said surface layer and first semiconductor substrate forming a base-collector semiconductor junction in said first portion of said body; a second semiconductive region iN a second portion of said body, said second region being of said second conductivity type and extending from the surface of said body into said surface layer and terminating short of said first semiconductor substrate; and a third semiconductive region of said first conductivity type extending from the surface of said body into said second semiconductive region, said second semiconductive region and said surface layer forming a base-collector semiconductor junction and said third region and said second region forming an emitter-base semiconductor junction in said second portion of said body.

Claim 11

A semiconductor device comprising: a body including a first semiconductor substrate of a first conductivity type and a surface layer of semiconductive type material of the same conductivity type disposed on said first semiconductor substrate, said surface layer having a resistivity substantially lower than the resistivity of said first semiconductor substrate; a first semiconductive region of a second conductivity type and extending from the surface of the body through said surface layer and into said first semiconductor substrate, said first semiconductive region and said surface layer and first semiconductor substrate forming a base-collector semiconductor junction in said first portion of said body; a second semiconductive region iN a second portion of said body, said second region being of said second conductivity type and extending from the surface of said body into said surface layer and terminating short of said first semiconductor substrate; and a third semiconductive region of said first conductivity type extending from the surface of said body into said second semiconductive region, said second semiconductive region and said surface layer forming a base-collector semiconductor junction and said third region and said second region forming an emitter-base semiconductor junction in said second portion of said body.

Claim 12

The semiconductor device of claim 9 including a second semiconductor substrate of said first conductivity type below said first semiconductor substrate, said second semiconductor substrate being of substantially lower resistivity than said first semiconductor substrate; a buried layer of said first conductivity type and of substantially lower resistivity than said first semiconductor substrate, said buried layer being between said first semiconductor substrate and said surface layer in said second portion of the body; and a connecting layer of low resistivity material of said first conductivity type coupling said buried layer to said second semiconductor substrate.

Claim 13

The device of claim 10 wherein said connecting layer is located on the surface of a pocket extending from the surface of the body down through said surface layer, said buried layer, said first semiconductor substrate and into said second semiconductor substrate.

Claim 14

The device as in claim 9 wherein a thin buried layer of heavily doped high conductivity N type material is formed between said first semiconductor substrate and said surface layer in said another portion of said body.