Monolithic Micro LED Array Structure for Low-Recombination High Resolution
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Solution Overview
Problem
Micro LED arrays face challenges with high integration density, smaller LEDs, and smaller pitch due to issues like surface recombination and non-radiative recombination, which affect light emission efficiency and reliability.
Innovation Solution
A method for forming monolithic LED array precursors with specific semiconductor layer growth and masking techniques to create electronically isolated LED structures, where electrical contacts are provided only on specific areas, reducing non-radiative recombination and enhancing light emission properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phosphor materials are used for wavelength conversion, then large pitch and low resolution arrays can be achieved, but higher resolution applications cannot be satisfied
Solution Approach 1:
The patent changes the material parameter from conventional phosphor to quantum dot-based wavelength converting materials, which have different optical properties that enable higher resolution applications while maintaining adaptability across different pitch sizes
2Reliability
If etching process is used to form perimeter of active region, then electrical isolation of micro LEDs is achieved, but surface recombination and non-radiative recombination increase
Solution Approach 1:
The patent converts the harmful effect of increased surface area from etching into a benefit by applying perimeter coverage with passivation layers, which reduce dangling bonds and non-radiative recombination at the etched surfaces, thereby recovering the energy loss caused by the etching process
3Measurement precision
If micro LED size is reduced for higher integration density, then array resolution improves, but surface recombination becomes more significant
Solution Approach 1:
The patent applies passivation layers to change the surface properties of micro LEDs, reducing surface recombination losses that become increasingly significant as device size is reduced for higher resolution applications
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 method results in improved light emission properties and reduced non-radiative recombination, achieving higher integration density and efficiency in micro LED arrays with enhanced reliability and performance.
Implementation Method 1
tuning of the amount of radiative recombination within each micro LED in the array
Implementation Method 2
The material in the mask is such that at the growth conditions, no additional material is grown directly on the mask but only inside apertures exposing portions of the surface of the underlying buffer layer
Implementation Method 3
improve light extraction from the array precursor
Data Source
Figure 1a~1b
Figure 2~3
Figure 4a~4c
AI summary
The present invention provides a monolithic LED array precursor comprising: a plurality of LED structures sharing a first semiconductor layer, wherein the first semiconductor layer defines a plane of the LED array precursor, each LED structure comprising: (i) a second semiconductor layer on the first semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the second semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the second semiconductor layer has sloped sides; (ii) a third semiconductor layer on the second semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the third semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the third semiconductor layer has sloped sides parallel to the sloped sides of the second semiconductor layer; (iii) a fourth semiconductor layer on the third semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the fourth semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the fourth semiconductor layer has sloped sides parallel to the sloped sides of the third semiconductor layer; and (iv) a primary electrical contact on the fourth semiconductor layer, wherein the contact is only on the upper surface portion of the fourth semiconductor layer which is parallel to the plane of the LED array precursor; wherein the third semiconductor layer comprises a plurality of quantum well sub-layers, the quantum well sub-layers having a greater thickness on a portion parallel to the plane of the LED array precursor and a reduced thickness on a portion which is not parallel to the plane of the LED array precursor.