Phototransistor having a buried base

Claim 2

A semiconductor phototransistor comprising: a. a semiconductor body of one conductivity type providing a collector region of said phototransistor and having first and second plane surfaces on opposites sides thereof; b. a layer of insulating material substantially transparent to incident optical radiation covering said first surface; c. a thin island region of opposite conductivity type wholly disposed within said semiconductor body in closely spaced relation with said first surface and spaced a greater distance from said second surface, said thin island region defining a buried base region completely surrounded by semiconductor material of said one conductivity type; d. said semiconductor material of said one conductivity type including a thin layer overlying said island region, said thin layer having a predetermined thickness and a predetermined dopant concentration to produce a selected sheet resistance of said thin layer, e. first electrode means disposed on said insulating layer and making ohmic contact with a small area of said thin layer through an aperture in said insulating layer; f. second electrode means on and ohmically connected with said second surface, and g. said island region having an area directly beneath said first electrode means that together with a contiguous area of said thin layer defines a base-emitter junction of said phototransistor, and the junction between the remainder of said island region and contiguous semiconductor material of said one conductivity type defining a photodetecting base-collector junction of said phototransistor.

Claim 3

A semiconductor phototransistor comprising: a. a semiconductor body of one conductivity type providing a collector region for said phototransistor and having first and second plane surfaces on opposite sides thereof, b. a layer of insulating material substantially transparent to incident optical radiation convering said first surface; c. a thin island region of opposite conductivity type wholly disposed within said semiconductor body in closely spaced relation with said first surface and spaced a greater distance from said second surface, said thin island region defining a buried base region completely surrounded by semiconductor material of said one conductivity type; d. a small area region of said opposite conductivity type extending from said first surface into said thin island region to define an emitter-base junction of said phototransistor; e. said semiconductor material of said one conductivity type including a thin layer overlying said island region and surrounding said small area region of said opposite conductivity type, said thin layer defining part of said first plane surface and having a predetermined thickness and predetermined dopant concentration producing a selected sheet resistance of said thin layer; f. first electrode means disposed on said insulating layer and making ohmic contact with said small area region through an aperture in said insulating layer; g. second electrode means on and ohmically connected with said second surface, and h. said island region and contiguous semiconductor material of said one conductivity type other than that of said small area region defining a photodetecting base-collector region junction of said phototransistor.

Claim 4

A semiconductor phototransistor comprising: a. a semiconductor body of one conductivity type providing a collector region for said phototransistor and having first and second plane surfaces on opposite sides thereof, b. a layer of insulating material substantially transparent to incident optical radiation convering said first surface; c. a thin island region of opposite conductivity type wholly disposed within said semiconductor body in closely spaced relation with said first surface and spaced a greater distance from said second surface, said thin island region defining a buried base region completely surrounded by semiconductor material of said one conductivity type; d. a small area region of said opposite conductivity type extending from said first surface into said thin island region to define an emitter-base junction of said phototransistor; e. said semiconductor material of said one conductivity type including a thin layer overlying said island region and surrounding said small area region of said opposite conductivity type, said thin layer defining part of said first plane surface and having a predetermined thickness and predetermined dopant concentration producing a selected sheet resistance of said thin layer; f. first electrode means disposed on said insulating layer and making ohmic contact with said small area region through an aperture in said insulating layer; g. second electrode means on and ohmically connected with said second surface, and h. said island region and contiguous semiconductor material of said one conductivity type other than that of said small area region defining a photodetecting base-collector region junction of said phototransistor.

Claim 5

A semiconductor phototransistor comprising: a. a semiconductor body of one conductivity type providing a collector region of said phototransistor and having first and second plane surfaces on opposite sides thereof; b. a layer of insulating material substantially transparent to inciDent optical radiation on said first surface, said layer of insulating material having an aperture therein; c. a thin island region of one conductivity type wholly located within said semiconductor body in closely spaced relation with the parallel to said first surface and spaced a greater distance from said second surface, said thin island region defining a buried base region completely surrounded by semiconductor material of said one conductivity type; d. said semiconductor material of said one conductivity type including a thin layer overlying said island region and providing part of said first plane surface, said thin layer having a predetermined thickness and a predetermined dopant concentration to produce a selected sheet resistance of said thin layer, e. first electrode means disposed on said insulating layer and making ohmic contact with a small area of said thin layer through said aperture therein, f. second electrode means on and ohmically connected with said second plane surface, and g. the junction between an area of said thin island region immediately beneath said first electrode means and a contiguous area of said thin layer defining a base-emitter junction of said phototransistor, and the junction between the remainder of said thin island region and contiguous semiconductor material of said one conductivity type defining a photodetecting base-collector junction of said phototransistor; h. said selected sheet resistance of said thin layer being such that responsive to a selective bias voltage across said first and second electrode means, current flow adjacent said first electrode means occurs radially through said thin layer causing a significant voltage drop in said thin layer adjacent said first electrode means to cause (i) forward biasing of said baseemitter junction and (ii) reverse biasing of the said base-collector junction emitter junction and (ii) reverse biasing of the said base-collector junction of said phototransistor.

Claim 6

A semiconductor phototransistor comprising: a. a semiconductor body of one conductivity type providing a collector region of said phototransistor and having first and second plane surfaces on opposite sides thereof; b. a layer of insulating material substantially transparent to inciDent optical radiation on said first surface, said layer of insulating material having an aperture therein; c. a thin island region of one conductivity type wholly located within said semiconductor body in closely spaced relation with the parallel to said first surface and spaced a greater distance from said second surface, said thin island region defining a buried base region completely surrounded by semiconductor material of said one conductivity type; d. said semiconductor material of said one conductivity type including a thin layer overlying said island region and providing part of said first plane surface, said thin layer having a predetermined thickness and a predetermined dopant concentration to produce a selected sheet resistance of said thin layer, e. first electrode means disposed on said insulating layer and making ohmic contact with a small area of said thin layer through said aperture therein, f. second electrode means on and ohmically connected with said second plane surface, and g. the junction between an area of said thin island region immediately beneath said first electrode means and a contiguous area of said thin layer defining a base-emitter junction of said phototransistor, and the junction between the remainder of said thin island region and contiguous semiconductor material of said one conductivity type defining a photodetecting base-collector junction of said phototransistor; h. said selected sheet resistance of said thin layer being such that responsive to a selective bias voltage across said first and second electrode means, current flow adjacent said first electrode means occurs radially through said thin layer causing a significant voltage drop in said thin layer adjacent said first electrode means to cause (i) forward biasing of said baseemitter junction and (ii) reverse biasing of the said base-collector junction emitter junction and (ii) reverse biasing of the said base-collector junction of said phototransistor.

Claim 7

The semiconductor phototransistor of claim 1 wherein said electrode means is disposed directly above the central region of said island region and contacts a small area of said thin layer.

Claim 8

The semiconductor phototransistor of claim 4, wherein said one conductivity type is N-type and said opposite conductivity type is P-type.

Claim 9

The semiconductor phototransistor of claim 5 wherein said second electrode means includes an N+ layer on said second surface of said semiconductor body.

Claim 10

The semiconductor phototransistor of claim 2 wherein said second electrode means comprises a more highly doped layer of said one conductivity type disposed upon said second surface of said semiconductor body.

Claim 11

The semiconductor phototransistor of claim 2 wherein said first electrode means is centered over said island region.

Claim 12

The semiconductor phototransistor of claim 8, wherein said one conductivity type is N-type and said opposite conductivity type is P-type.