Compact RGB Pixel Arrays With Dual p-n Junction Color Control
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Solution Overview
Problem
Current monolithic RGB LED arrays face challenges in high-resolution displays due to limited space for mesa etches and terminals, and existing approaches require excessive voltage or filters for color control, leading to inefficiencies in power consumption and color purity.
Innovation Solution
The development of a micro-LED array with a reduced number of mesa etching steps and contact terminals, utilizing a reflective p-contact electrode bonded to a backplane, and featuring a dielectric layer with conformal metal deposits, allows for bias-based control of color emission through voltage, enabling efficient and low-power color shifting with reverse polarity LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current monolithic RGB LED array designs are used, then color emission is achieved, but the number of required terminals and mesa etching steps increases device complexity and consumes limited display space
Solution Approach 1:
The patent combines multiple functions into shared structures: a single common p-contact electrode serves as the anode for multiple LEDs, and a shared dielectric layer with conformal metal deposits provides both electrical isolation and reflective functionality. This merging approach reduces the total number of separate terminals and etching steps required, directly addressing the contradiction between device complexity and display space.
Solution Approach 2:
The common p-contact electrode performs multiple functions: it serves as the electrical anode for all LEDs in the array, provides a reflective surface for light extraction, and acts as a structural support element. The dielectric layer similarly provides both electrical isolation and optical reflection. This multi-functionality reduces the number of dedicated components, thereby reducing device complexity while maintaining full functionality within limited display space.
2Ease of manufacture
If single p-n junction with quantum wells is used, then fabrication is simplified, but excess voltage across the active region increases power consumption
Solution Approach 1:
The patent divides the single p-n junction into multiple stacked p-n junctions, each with its own active region and quantum wells. This segmentation allows each junction to operate at a lower, more efficient voltage while maintaining the ability to produce multiple colors through selective excitation. The segmented structure preserves fabrication simplicity while eliminating the excess voltage problem of single-junction designs.
Solution Approach 2:
The patent transitions from a lateral arrangement of quantum wells in a single junction to a vertical stacking of multiple junctions with their respective active regions. This dimensional change from lateral to vertical organization allows independent voltage control of each junction while maintaining compact structure, thereby reducing power consumption without complicating fabrication.
3Ease of manufacture
If single p-n junction with quantum wells is used, then fabrication is simplified, but filters are required which reduces color purity
Solution Approach 1:
By segmenting the device into multiple p-n junctions with distinct active regions, each junction can be engineered to emit a specific color with high purity. The segmented architecture eliminates the need for filters because each junction naturally emits its designated color, thereby maintaining both ease of fabrication and high color purity.
Solution Approach 2:
The patent applies local quality by designing each active region with specific quantum well compositions and thicknesses tailored to emit a particular color. This localized optimization of material properties in each junction ensures high color purity without requiring filters, while the overall structure remains fabrication-friendly through the systematic stacking approach.
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 enables better control over emission color, reduces power consumption, and simplifies the manufacturing process by requiring fewer terminals and etching steps, while maintaining high color purity and efficiency in micro-LED displays.
Implementation Method 1
the first n-type layer on a first tunnel junction, the first tunnel junction on a first p-type layer... on a second tunnel junction, the second tunnel junction on a second p-type layer
Implementation Method 2
a reflective p-contact electrode bonded to a backplane... a conformal reflective metal layer on the dielectric layer
Data Source
AI summary
Provided is a monolithically integrated red green blue (RGB) light emitting diode (LED) array manufactured with a reduced number of mesa etching steps and contact terminals. The LED array may have two or three p-n-junctions grown sequentially on a wafer. One of the p-n junctions has the opposite order of deposition of the n- and p-layers. A light-emitting active region is embedded between the n- and p-layers of each of the p-n junctions. Each active region emits light of different wavelength. The wafer is etched into multi-level mesas, creating two separate voltage terminals and a ground contact to control the bias between particular semiconductor layers. All of the p-n junctions share a common ground contact.