Externally Strained Semiconductor Devices for QCSE Mitigation

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Solution Overview

Problem

Current solid-state lighting and electronic devices face challenges such as reduced radiative recombination rates and efficiency droop due to quantum-confined Stark effect (QCSE) and limited control over polarization effects, which affect the performance of LEDs and transistors, especially in high-voltage and high-current applications.

Innovation Solution

The application of external strain to semiconductor devices, such as LEDs and FETs, to induce a predetermined amount of strain that modifies their band structure, improving quantum efficiency, tunability of emission wavelengths, and enabling strain-effect transistors that modulate electrical currents without gate bias, thereby overcoming QCSE and enhancing performance in next-generation lighting and power electronics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If external strain is applied to modify band structure and improve quantum efficiency, then internal quantum efficiency is enhanced, but device structure becomes more complex

Engineering Contradiction:

Improveinternal quantum efficiencyVSAvoiddevice structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies external strain as a controllable parameter to modify the band structure of semiconductor materials. By changing the strain parameter (tensile or compressive), the bandgap and carrier distribution are adjusted, thereby improving internal quantum efficiency without fundamentally changing the device architecture

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent pre-applies strain to the semiconductor device during fabrication or operation to establish optimal band alignment before the device begins its primary function. This preliminary strain application ensures that the device operates at peak efficiency from the start, avoiding the need for complex real-time adjustment mechanisms

Inventive Principle:

Principle #10Preliminary action

2Power

If quantum-confined Stark effect is present in high-voltage devices, then device functionality is enabled, but radiative recombination rates are reduced

Engineering Contradiction:

Improvehigh-voltage capabilityVSAvoidradiative recombination rates

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent applies external strain in advance to counteract the quantum-confined Stark effect that would otherwise occur during high-voltage operation. By pre-establishing a strain field that opposes the QCSE-induced band tilting, the patent prevents the separation of electron and hole wavefunctions, thereby maintaining high radiative recombination rates even under high-voltage conditions

Inventive Principle:

Principle #9Preliminary anti-action

3Ease of manufacture

If semiconductor layers are disposed in contact with packaging substrate, then device assembly is simplified, but strain retention may be compromised

Engineering Contradiction:

Improvedevice assemblyVSAvoidstrain retention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces a strain-maintaining structure or intermediate layer between the semiconductor layers and the packaging substrate. This intermediary component serves as a strain reservoir or transmission medium that preserves the externally applied strain while allowing the device to be properly assembled and mounted on the substrate

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach enhances the internal quantum efficiency of LEDs, allows for color tunability, and enables normally-off transistor operation, improving the performance and efficiency of solid-state lighting and power electronics by mitigating QCSE and providing flexible strain modulation for enhanced functionality.

Implementation Method 1

The externally applied strain modifies the band structure of the light-emitting device

Methodology Applied

Scientific EffectBand structure modification:

Implementation Method 2

the overlap between the electron and hole wavefunctions is enhanced thereby increasing the radiative recombination rates

Methodology Applied

Scientific EffectWavefunction overlap enhancement:

Implementation Method 3

the externally applied strain can be used to counteract the quantum-confined stark effect

Methodology Applied

Scientific EffectQuantum-confined Stark effect mitigation:

Implementation Method 4

the band tilting in a quantum well

Methodology Applied

Scientific EffectBand tilting reduction:

Implementation Method 5

The layered structure is in one of a bend-up or bend-down condition and comprises a predetermined amount of strain

Methodology Applied

Scientific EffectStrain-induced bending: Elasticity

Data Source

PatentUS10897120B2Externally-strain-engineered semiconductor photonic and electronic devices and assemblies and methods of making same

Publication Date: 2021.01.19 UNIV HOUSTON SYST

AI summary

Externally-strained devices such as LED and FET structures as discussed herein may have strain applied before or during their being coupled to a housing or packaging substrate. The packaging substrate may also be strained prior to receiving the structure. The strain on the devices enables modulation of light intensity, color, and electrical currents in some embodiments, and in alternate embodiments, enables a fixed strain to be induced and maintained in the structures.