Micro-LED Edge Bandgap Tuning to Reduce Surface Recombination
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Solution Overview
Problem
Micro-LEDs suffer from significant surface recombination losses due to their small size, where electrons diffuse and are lost at the interface, reducing efficiency, especially when the diffusion length approaches the chip's linear dimension.
Innovation Solution
Increasing the bandgap in the outer region of a semiconductor layer by ion implantation and subsequent annealing to intermix ions with atoms, which reduces lateral carrier mobility and surface recombination, while maintaining a light outcoupling surface diameter less than twice the electron diffusion length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the chip size is reduced to create micro-LEDs, then the device can achieve higher pixel density and smaller form factor, but surface recombination losses increase significantly reducing efficiency
Solution Approach 1:
The patent applies local quality by creating a graded bandgap structure where the bandgap energy varies spatially across the semiconductor layer. The outer region has a higher bandgap than the central region, which is achieved through controlled composition gradients in alloy semiconductors. This local variation in bandgap energy confines carriers to the central region where light emission occurs, preventing surface recombination at the edges while maintaining the small overall device size.
2Loss of energy
If ion implantation and annealing are used to increase bandgap in outer region, then surface recombination is reduced and efficiency increases, but device complexity and manufacturing process complexity increase
Solution Approach 1:
The patent employs parameter changes by modifying the bandgap energy parameter through ion implantation followed by thermal annealing. The ion implantation introduces defects and compositional changes that, when annealed, create a permanent increase in bandgap energy in the outer region of the semiconductor layer. This parameter modification approach allows control of carrier distribution without adding physical structural complexity to the device.
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 approach effectively reduces surface recombination losses in micro-LEDs, enhancing their efficiency and brightness by funneling current vertically through the central region and reducing electron diffusion, thereby increasing the internal quantum efficiency.
Implementation Method 1
a semiconductor layer having an active light emitting layer
Implementation Method 2
by implanting ions in the outer region of the semiconductor layer and subsequently annealing the outer region of the semiconductor layer to intermix the ions with atoms within the outer region of the semiconductor layer
Data Source
AI summary
Disclosed herein are systems and methods for reducing surface recombination losses in micro-LEDs. In some embodiments, a method of forming an LED involves forming a semiconductor structure on a substrate. The semiconductor structure includes a p-side semiconductor layer, an n-side semiconductor layer, and an active light emitting layer between the p-side semiconductor layer and the n-side semiconductor layer. The semiconductor structure is also formed to include a light outcoupling surface facing the substrate. The light outcoupling surface has a diameter less than twice an electron diffusion length of a material of the semiconductor structure. The method further involves implanting ions in an outer region of the semiconductor structure, then annealing the outer region after the ions have been implanted. The annealing causes the ions to intermix with atoms within the outer region, thereby increasing a bandgap of the outer region.