Heterojunction Bipolar Transistor Low Voltage RF Gain

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional heterojunction bipolar transistors face challenges in achieving high radio frequency (RF) gain at lower supply voltages, as the base-collector junction becomes forward-biased, increasing capacitance and reducing RF performance.

Innovation Solution

A heterojunction bipolar transistor design where the base-collector junction is configured to become forward-biased at a higher turn-on voltage than the base-emitter junction, maintaining a wider depletion region and reducing capacitance, thereby enhancing RF gain at lower supply voltages. This is achieved by varying the bandgap energies and doping concentrations across the collector and base materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a conventional single heterojunction bipolar transistor is used, then desirable DC gain is achieved at higher supply voltages, but high DC gain is not provided at lower supply voltages

Engineering Contradiction:

ImproveDC gainVSAvoidsupply voltage

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The patent applies local quality by creating different heterojunctions at different locations within the transistor. The first heterojunction (emitter-base) uses materials with one bandgap configuration optimized for low-voltage operation, while the second heterojunction (base-collector) uses materials with a different bandgap configuration optimized for maintaining high DC gain. This spatial differentiation of material properties allows the transistor to achieve both low-voltage operation and high DC gain simultaneously.

Inventive Principle:

Principle #3Local quality

2Power

If a conventional double heterojunction bipolar transistor is used, then high DC gain is provided at both higher and lower supply voltages, but high RF gain is not achieved at lower supply voltages

Engineering Contradiction:

ImproveDC gainVSAvoidRF gain

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If the base-collector junction becomes forward-biased at lower supply voltages, then operation at lower voltages is enabled, but capacitance increases and RF performance is reduced

Engineering Contradiction:

Improvesupply voltageVSAvoidRF performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies parameter changes by carefully selecting and varying the bandgap energies of the semiconductor materials used in different junctions. The first heterojunction uses materials with a smaller bandgap difference to enable low-voltage operation, while the second heterojunction uses materials with a larger bandgap difference to maintain reverse bias and low capacitance. This parameter optimization allows the transistor to operate at low voltages while maintaining high RF performance.

Inventive Principle:

Principle #35Parameter changes

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

The design results in improved RF gain at lower supply voltages by maintaining the base-collector junction in a reverse-biased state, reducing capacitance and negative feedback, and increasing RF performance compared to conventional transistors.

Implementation Method 1

maintaining a wider depletion region and reducing capacitance

Methodology Applied

Scientific EffectDepletion region: Capacitance

Implementation Method 2

The base-collector junction is configured to become forward-biased at a first turn-on voltage. The base-emitter junction is configured to become forward-biased at a second turn-on voltage

Methodology Applied

Scientific EffectForward bias: Diode

Implementation Method 3

The emitter has a bandgap near the base-emitter junction approximately equal to 1.32 electronvolts (eV), and the collector has a bandgap near the base-collector junction that is approximately equal to 1.42 eV

Methodology Applied

Scientific EffectBandgap energy:

Implementation Method 4

The present disclosure relates to heterojunction bipolar transistors for improved radio frequency (RF) performance

Methodology Applied

Scientific EffectHeterojunction:

Data Source

PatentUS9502510B2Heterojunction bipolar transistors for improved radio frequency (RF) performance

Publication Date: 2016.11.22 QORVO US INC

AI summary

The present disclosure relates to heterojunction bipolar transistors for improved radio frequency (RF) performance. In this regard, a heterojunction bipolar transistor includes a base, an emitter, and a collector. The base is formed over the collector such that a base-collector junction is formed between the base and the collector. The base-collector junction is configured to become forward-biased at a first turn-on voltage. The emitter is formed over the base such that a base-emitter junction is formed between the base and the emitter. The base-emitter junction is configured to become forward-biased at a second turn-on voltage, as opposed to the first turn-on voltage. Notably, the second turn-on voltage is lower than the first turn-on voltage.