Mesa Sidewall Oxide Passivation for Micro-LED Efficiency
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Solution Overview
Problem
Optoelectronic devices, particularly micro-LEDs, suffer from poor efficiency due to high density of defects on mesa sidewalls caused by uncontrolled oxidation, leading to non-radiative recombination and leakage current, which reduces internal quantum efficiency and operating lifetime.
Innovation Solution
A method involving the removal of at least 75% of native oxides from the mesa structure surfaces before applying a group III-dominant terminating oxide layer, followed by optional group III-dominant overcoating, to improve surface quality and reduce non-radiative recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If mesa structure is formed by etching and lithography techniques, then device miniaturization is achieved, but high density of atomic level defects and structural disorder are generated on sidewalls
Solution Approach 1:
The patent applies preliminary action by performing surface cleaning and passivation treatments on the mesa sidewalls before subsequent processing steps. Specifically, the sidewalls are cleaned to remove native oxides and then passivated with a dielectric material to prevent defect formation before any further device fabrication steps occur.
Solution Approach 2:
The patent introduces an intermediary substance (dielectric passivation material) between the defective sidewall surface and the subsequent processing steps. This intermediary layer acts as a barrier that prevents the propagation of defects into the active device regions while allowing the miniaturized structure to function properly.
2Reliability
If native oxides are present on mesa sidewalls, then surface passivation is provided, but non-radiative Shockley-Read-Hall recombination and leakage current increase
Solution Approach 1:
The patent applies the taking out principle by selectively removing native oxides from the mesa sidewalls through a cleaning step. This extraction of the harmful native oxide layer eliminates the source of non-radiative recombination centers while the subsequent dielectric passivation provides the necessary surface protection without the detrimental effects of native oxides.
Solution Approach 2:
The patent converts the harmful effect of native oxides (which provide uncontrolled passivation with high defect density) into a benefit by first removing them to create a clean surface, then applying a controlled dielectric passivation layer that provides the same protective function without the non-radiative recombination problems.
3Length of moving object
If charge carrier diffusion length is comparable to micro-LED size, then device scaling is achieved, but impact of defective sidewall extends over large distances affecting entire chip performance
Solution Approach 1:
The dielectric passivation layer serves as an intermediary barrier that prevents the extension of defect effects from the sidewalls into the bulk active regions. This intermediary layer effectively isolates the charged carriers from the defective sidewall regions, preventing the propagation of non-radiative recombination effects across the device.
Solution Approach 2:
The patent employs a thin film dielectric passivation layer that conformally coats the mesa sidewalls. This thin film acts as a flexible protective shell that follows the contours of the miniaturized structure while providing continuous protection against defect-mediated recombination throughout the device volume.
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
Enhances the internal quantum efficiency and reduces carrier leakage, improving the performance and longevity of optoelectronic devices by minimizing defects and enhancing carrier confinement.
Implementation Method 1
cleaning the first surface of the mesa structure by removing at least 75% of native oxides on the first surface of the mesa structure
Implementation Method 2
forming a first terminating oxide layer of a first type on the first surface of the mesa structure
Data Source
AI summary
The aspects of the disclosed embodiments relates to an optoelectronic device including a substrate layer having a first surface plane and a second surface plane opposite and parallel to the first surface plane. The device also includes a mesa structure arranged on the first surface plane of the substrate layer. The mesa structure includes at least one layer of material; and a first surface arranged at an angle α with respect to the first surface plane of the substrate layer, wherein the angle α is different from 0° and 180°. The device still further includes a first terminating oxide layer of a first type arranged on the first surface of the mesa structure and the first surface of the mesa structure has been cleaned by removing at least 75% of native oxides on the first surface of the mesa structure before arranging the first terminating oxide layer of a first type thereon.