Micro-LED Field-Effect Isolation for Sidewall Recombination Loss
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Solution Overview
Problem
Micro-LEDs suffer from high non-radiative recombination rates due to defects at the sidewalls of mesa structures, leading to reduced efficiency, particularly as device sizes decrease, exacerbated by high surface recombination velocities in materials like AlGaInP.
Innovation Solution
Implement field-effect isolations by applying an electric field through a gate grid and insulator grid to deplete holes and accumulate electrons in the active layers, isolating individual micro-LEDs to reduce non-radiative recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mesa structures are used to define individual micro-LEDs, then device isolation is achieved, but non-radiative recombination increases due to sidewall defects
Solution Approach 1:
An insulator layer is introduced as an intermediary between the mesa structures to electrically isolate adjacent micro-LEDs. This insulator prevents carrier diffusion across sidewalls while minimizing exposure to defect-induced non-radiative recombination pathways.
Solution Approach 2:
Physical/chemical isolation methods (mesa etching) are replaced with electrical isolation using field-effect. A gate electrode applies an electric field to deplete carriers near sidewalls, substituting mechanical structure modification with an electrical control mechanism that reduces sidewall defect impact.
2Productivity
If device size is reduced to increase packing density, then resolution improves, but non-radiative recombination rates increase due to higher surface-to-volume ratio
Solution Approach 1:
Field-effect isolation replaces physical mesa structures with an electrical isolation mechanism. This allows smaller device sizes with higher packing density while maintaining isolation effectiveness, as the electrical field can be applied uniformly without requiring large physical separation distances.
Solution Approach 2:
The isolation mechanism transitions from a static physical structure to a dynamically controllable electrical field. By adjusting gate voltage, the depletion region width can be optimized for each device size, allowing effective isolation even in sub-10-micron devices where physical isolation would be impractical.
3Loss of energy
If field-effect isolation is applied to reduce non-radiative recombination, then quantum efficiency improves, but device complexity increases due to additional gate and insulator structures
Solution Approach 1:
The gate electrode structure serves multiple functions: it provides electrical isolation between adjacent micro-LEDs, controls carrier distribution to reduce sidewall recombination, and can potentially serve as part of the driving circuitry. This multi-functionality reduces the need for separate isolation structures.
Solution Approach 2:
The insulator layer is integrated into the existing mesa structure fabrication process, combining the isolation function with the device formation steps. This merging of functions reduces process complexity and avoids adding separate isolation fabrication steps.
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
Significantly improves quantum efficiencies of micro-LEDs by minimizing defect-induced non-radiative recombination, especially in small pitch and small active region devices.
Implementation Method 1
a gate grid coupled to the insulator grid and configured to apply an electric field through the insulator grid to the plurality of semiconductor epitaxial layers in the regions between the individual electrodes of the array of electrodes to electrically isolate the plurality of semiconductor epitaxial layers into individual micro-LEDs
Implementation Method 2
a quantum well layer configured to emit light
Implementation Method 3
Light emitting diodes (LEDs) convert electrical energy into optical energy
Data Source
AI summary
A micro-light emitting diode (micro-LED) device includes a plurality of semiconductor epitaxial layers that includes a quantum well layer configured to emit light. The micro-LED device also includes an array of electrodes for an array of micro-LEDs, the array of electrodes coupled to the plurality of semiconductor epitaxial layers. The micro-LED device further includes an insulator grid coupled to the plurality of semiconductor epitaxial layers and positioned in regions between individual electrodes of the array of electrodes, and a gate grid coupled to the insulator grid and configured to apply an electric field through the insulator grid to the plurality of semiconductor epitaxial layers in the regions between the individual electrodes of the array of electrodes to electrically isolate the plurality of semiconductor epitaxial layers into individual micro-LEDs of the array of micro-LEDs.