Complementary Lateral Bipolar Junction Transistors for Radiation Sensing

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Solution Overview

Problem

Conventional sensors, such as Geiger counters and personal radiation dosimeters, face limitations in measuring high radiation rates and providing real-time indications of radiation levels, while solid-state sensors lack sufficient sensitivity and resolution due to limited amplification capabilities.

Innovation Solution

The development of complementary lateral bipolar junction transistor (LBJT) structures with opposite polarities, integrated on a common substrate, which include a sensing structure and amplifying transistors to generate and amplify signals indicative of environmental properties like radiation, enabling effective detection and amplification of high-energy particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional solid-state sensors are used, then compactness and cost efficiency are improved, but sensitivity and resolution are limited due to inability to amplify output currents

Engineering Contradiction:

Improvesensitivity and resolutionVSAvoidadditional circuit design for amplification

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the sensing function and signal amplification function into a single integrated device. The bipolar junction transistor serves dual purposes: its structure detects radiation-induced charge changes while simultaneously providing current amplification through its inherent transistor action, eliminating the need for separate amplification circuits

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bipolar junction transistor is designed to perform multiple functions within a single device structure. It acts as both the radiation sensing element (detecting charge changes in the insulating layer) and the signal amplification element (providing current gain through base-emitter-collector current relationships), thereby reducing overall device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If Geiger counters are used for radiation detection, then real-time readout is provided, but measurement of high radiation rates and energy measurement are limited

Engineering Contradiction:

Improvereal-time measurement capabilityVSAvoidhigh radiation rate measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from counting discrete ionization events (Geiger counter approach) to measuring continuous charge accumulation in an insulating layer. This parameter change enables the sensor to handle high radiation rates without saturation while maintaining real-time measurement capability, as the charge buildup rate directly reflects the radiation flux

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If personal radiation dosimeters are used, then portability is improved, but real-time indication of radiation levels cannot be provided

Engineering Contradiction:

ImproveportabilityVSAvoidreadout time delay

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent implements continuous real-time monitoring by maintaining the bipolar transistor in an active state that continuously converts charge changes in the insulating layer into amplified output signals. This continuous operation eliminates readout delays while preserving portability, as the device provides immediate feedback on radiation levels without requiring laboratory equipment or processing time

Inventive Principle:

Principle #20Continuity of useful action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution provides enhanced sensitivity and resolution for radiation detection, offering real-time monitoring and amplification of sensing signals, improving the portability and accuracy of radiation sensors without being affected by charges created by ionizing radiation.

Implementation Method 1

the first lateral bipolar junction transistor is configured to generate an output signal indicative of a change in stored charge in the sensing structure resulting from a presence of an environmental property

Methodology Applied

Scientific EffectIonizing radiation: Ionisation

Implementation Method 2

change in stored charge in the sensing structure

Methodology Applied

Scientific EffectCharge storage: Capacitance

Implementation Method 3

The second lateral bipolar junction transistor is configured to amplify the output signal of the first lateral bipolar junction transistor

Methodology Applied

Scientific EffectBipolar junction transistor amplification:

Data Source

PatentUS9659979B2Sensors including complementary lateral bipolar junction transistors

Publication Date: 2017.05.23 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An integrated radiation sensor for detecting the presence of an environmental material and/or condition includes a sensing structure and first and second lateral bipolar junction transistors (BJTs) having opposite polarities. The first lateral BJT has a base that is electrically coupled to the sensing structure and is configured to generate an output signal indicative of a change in stored charge in the sensing structure. The second lateral BJT is configured to amplify the output signal of the first bipolar junction transistor. The first and second lateral BJTs, the sensing structure, and the substrate on which they are formed comprise a monolithic structure.