Semiconductor LED Lift-Off Structure to Prevent Leakage Current
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Solution Overview
Problem
Current display devices using semiconductor light-emitting diodes face challenges such as damage from heat or chemicals during separation from growth substrates, leading to increased manufacturing costs and surface leakage currents, particularly in LCDs and AMOLEDs.
Innovation Solution
A display device structure incorporating a porous material for mechanical lift-off and an aluminum oxide layer to prevent side surface etching, reducing leakage currents and manufacturing costs, while using an intermediate aluminum layer to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor light-emitting diodes are separated from growth substrate using conventional methods (heat or chemicals), then separation is achieved, but the diodes are damaged due to heat or chemicals
Solution Approach 1:
A porous sacrificial layer is introduced as an intermediary between the semiconductor light-emitting diode and the growth substrate. This sacrificial layer is selectively removed through electropolishing, enabling mechanical lift-off of the diode from the substrate without exposing it to damaging heat or chemicals. The porous structure allows efficient removal while protecting the diode integrity.
Solution Approach 2:
The patent replaces conventional thermal or chemical separation methods with a mechanical lift-off method. By forming a porous sacrificial layer that can be selectively removed through electropolishing, the diode is mechanically separated from the substrate without thermal or chemical damage, substituting harmful processes with a controlled mechanical removal approach.
2Reliability
If conventional separation methods are used, then separation is achieved, but manufacturing cost increases due to high facility cost
Solution Approach 1:
The patent employs a disposable porous sacrificial layer made of aluminum or aluminum alloy that is intentionally designed to be removed after serving its purpose of enabling diode separation. This sacrificial layer is inexpensive and single-use, replacing costly conventional separation facilities and processes with a low-cost consumable material approach.
3Reliability
If side surface etching occurs during electropolishing, then separation is achieved, but leakage current increases through side surface defects
Solution Approach 1:
A protective layer is formed on the side surfaces of the semiconductor light-emitting diode before the electropolishing process. This protective layer prevents side surface etching during electropolishing, thereby preventing the formation of defects that would generate leakage current. The protective action is applied in advance to counteract potential harmful effects of the electropolishing process.
Solution Approach 2:
The protective layer acts as an intermediary barrier between the electropolishing environment and the side surfaces of the diode. It selectively protects the side surfaces from etching while allowing the electropolishing process to proceed on the sacrificial layer, preventing direct contact between harmful electropolishing agents and the diode side surfaces that would cause leakage current.
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 solution effectively prevents damage to semiconductor light-emitting diodes during separation, reduces manufacturing costs, and improves the efficiency of the diodes by minimizing surface leakage currents and maintaining high luminance characteristics.
Implementation Method 1
a layer of a porous material allowing electropolishing is disposed and separated by a mechanical lift-off method when the semiconductor light-emitting diode is separated from the growth substrate
Implementation Method 2
an aluminum oxide layer covering a side surface of the intermediate layer to prevent side surface etching in an electropolishing step
Implementation Method 3
an intermediate layer containing aluminum between a second conductive semiconductor layer and the undoped semiconductor layer, and an aluminum oxide layer covering a side surface of the intermediate layer to prevent side surface etching in an electropolishing step and reduce leakage current through a side surface etching
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A display device according to the present invention has a plurality of semiconductor light-emitting diodes. At least one of the semiconductor light-emitting diodes has: a first conductive electrode and a second conductive electrode; a first conductive semiconductor layer on which the first conductive electrode is disposed; a second conductive semiconductor layer which overlaps the first conductive semiconductor layer and on which the second conductive electrode is disposed; an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; an undoped semiconductor layer disposed on the second conductive semiconductor layer; and protrusions formed from a porous material allowing electropolishing, on the undoped semiconductor layer.