Semipolar InGaN Yellow LEDs Overcoming Quantum-Confined Stark Effect
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Solution Overview
Problem
Conventional c-plane quantum well structures in III-nitride optoelectronic devices suffer from the quantum-confined Stark effect due to strong piezoelectric and spontaneous polarizations, limiting carrier recombination efficiency and wavelength emission, while growth on nonpolar or semipolar planes is challenging and not widely adopted.
Innovation Solution
Fabrication of yellow, amber, or red LEDs on semipolar (Al, In, Ga, B)N semiconductor crystals with high Indium composition and crystal quality, allowing for peak emission wavelengths longer than 560 nm and output powers greater than 3.5 mW at 20 mA, using metalorganic vapor deposition (MOCVD) on semipolar planes like {11-22}, which reduces internal electric fields and enables longer wavelength emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional c-plane quantum well structures are used, then manufacturing is well-established and easy, but strong piezoelectric and spontaneous polarizations cause quantum-confined Stark effect that limits carrier recombination efficiency and wavelength emission
Solution Approach 1:
The patent changes the crystallographic orientation parameter from conventional c-plane to semipolar planes (such as {11-22}, {10-11}, or {10-13}), which fundamentally alters the polarization characteristics. This parameter change reduces the strong piezoelectric and spontaneous polarizations present in c-plane structures, thereby eliminating the quantum-confined Stark effect and improving carrier recombination efficiency while enabling longer wavelength emissions.
2Reliability
If growth on nonpolar or semipolar planes is attempted, then polarization effects are reduced eliminating quantum-confined Stark effect, but growth remains challenging and is not widely adopted
Solution Approach 1:
The patent systematically optimizes growth parameters including temperature profiles, pressure conditions, and gas flow rates specifically for semipolar plane growth. By establishing refined parameter sets tailored to semipolar orientations, the patent makes the growth process more controllable and reproducible, reducing the challenge associated with non-conventional plane growth while maintaining the polarization benefits.
Solution Approach 2:
The patent introduces carefully designed intermediate buffer layers and transition structures that facilitate epitaxial growth on semipolar planes. These intermediary layers help manage the complex growth dynamics and reduce defects, serving as a bridge between the substrate and the active quantum well regions, thereby simplifying the overall manufacturing process.
3Illumination intensity
If high Indium composition is used in active layer, then peak emission wavelength extends beyond 560 nm achieving yellow light emission, but crystal quality may deteriorate
Solution Approach 1:
The patent optimizes growth parameters including lower growth temperatures, adjusted V/III ratios, and controlled Indium precursor flow rates to enable high Indium composition incorporation while maintaining crystal quality. These parameter changes allow the formation of stable InGaN quantum wells with high Indium content, achieving peak emissions beyond 560 nm without excessive defect formation.
Solution Approach 2:
The patent employs localized quality control strategies by optimizing the quantum well structure design, using composition gradients, and implementing targeted growth conditions in different regions of the active layer. This allows high Indium composition to be maintained in the quantum well regions for long wavelength emission while preserving overall crystal quality through localized structural optimizations.
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
Achieves high output power and extended wavelength emission in yellow LEDs, facilitating the development of high-power white LEDs and multi-color LEDs by combining blue, green, and yellow semipolar-based nitride LEDs, overcoming the limitations of c-plane nitride technology.
Implementation Method 1
using metalorganic vapor deposition (MOCVD) on semipolar planes like {11-22}
Implementation Method 2
conventional c-plane quantum well (QW) structures in III-nitride based optoelectronic and electronic devices suffer from the undesirable quantum-confined Stark effect (QCSE), due to the existence of strong piezoelectric and spontaneous polarizations
Implementation Method 3
conventional c-plane quantum well (QW) structures in III-nitride based optoelectronic and electronic devices suffer from the undesirable quantum-confined Stark effect (QCSE), due to the existence of strong piezoelectric and spontaneous polarizations
Implementation Method 4
conventional c-plane quantum well (QW) structures in III-nitride based optoelectronic and electronic devices suffer from the undesirable quantum-confined Stark effect (QCSE)
Implementation Method 5
Fabrication of yellow, amber, or red LEDs on semipolar (Al, In, Ga, B)N semiconductor crystals with high Indium composition and crystal quality, allowing for peak emission wavelengths longer than 560 nm and output powers greater than 3.5 mW at 20 mA
Data Source
AI summary
A yellow Light Emitting Diode (LED) with a peak emission wavelength in the range 560-580 nm is disclosed. The LED is grown on one or more III-nitride-based semipolar planes and an active layer of the LED is composed of indium (In) containing single or multi-quantum well structures. The LED quantum wells have a thickness in the range 2-7 nm. A multi-color LED or white LED comprised of at least one semipolar yellow LED is also disclosed.