Integrated LED Overvoltage Protector on Substrate Marginal Portion
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Solution Overview
Problem
Existing light-emitting semiconductor devices (LEDs) incorporating overvoltage protectors are bulky and inefficient due to the side-by-side arrangement of LEDs and protectors on sapphire substrates, leading to size increases and difficulties in setting desired forward voltages for the protectors.
Innovation Solution
An integrated semiconductor device that incorporates an overvoltage protector on the side surface of the light-generating semiconductor region, using a pn-junction diode or other devices like Schottky diodes, without increasing the size of the LED, by utilizing the marginal portion of the substrate for the protector, allowing for compact and efficient overvoltage protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LED and protector diode are arranged side-by-side on the sapphire substrate, then overvoltage protection is provided, but the device size increases
Solution Approach 1:
The patent merges the LED and protector diode into a single integrated structure by forming the protector diode on the same sapphire substrate as the LED. The p-type semiconductor layer and n-type semiconductor layer are grown epitaxially on adjacent regions of the substrate, sharing common electrical connection structures (electrodes and conductors), thereby providing overvoltage protection without requiring separate discrete components and reducing overall device footprint.
Solution Approach 2:
The sapphire substrate serves multiple functions: it acts as the base for both the LED and the protector diode, provides electrical isolation through its insulating properties, and serves as a platform for integrating both functional elements. The common electrodes and conductor layers serve dual purposes for both the LED and protector diode operations.
2Area of stationary object
If the LED size is reduced to maintain the same chip size with protector diode, then the optical output decreases
Solution Approach 1:
The LED and protector diode share common electrical connection structures including the first electrode, second electrode, and conductor layers. This merging of connection structures eliminates the need for separate dedicated conductors for each component, thereby maximizing the area available for the LED active region and maintaining high optical output within a compact chip footprint.
3Reliability
If additional conductors are provided to interconnect LED and protector diode, then overvoltage protection is achieved, but device complexity and size increase
Solution Approach 1:
The patent merges the electrical connection structures of the LED and protector diode by using common first and second electrodes and shared conductor layers. The p-type semiconductor layer and n-type semiconductor layer are electrically connected through these shared structures, eliminating the need for additional dedicated interconnection conductors and simplifying the overall device architecture.
Solution Approach 2:
The first electrode, second electrode, and conductor layers serve universal functions for both the LED and the protector diode. These structures provide electrical connections for current injection to the LED while simultaneously providing the reverse bias connection path for the protector diode during overvoltage conditions.
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 results in a more compact, cost-effective, and efficient light-emitting semiconductor device that maintains optical output intensity while providing protection against overvoltages without increasing the device size, enabling easier manufacturing and reduced material costs.
Implementation Method 1
They teach to build an overvoltage protector, which takes the form of a pn-junction diode, on the same sapphire substrate as the LED.
Implementation Method 2
The protector diode is forward biased, on the other hand, during application of a reverse voltage to the LED. Conduction is then initiated through the protector diode in response to a voltage not less than the predefined conduction-initiating voltage of the protector diode.
Data Source
AI summary
An LED incorporating an overvoltage protector with a minimum of space requirement. The LED itself comprises a p-type semiconductor substrate, a light-generating semiconductor region grown epitaxially thereon, a first electrode on the light-generating semiconductor region, and a second electrode on the underside of the substrate. The standard method of LED fabrication is such that the substrate is notionally divisible into a main portion in register with the overlying light-generating semiconductor region and, surrounding the main portion, a tubular marginal portion needed for dicing the wafer into individual squares or dice. The overvoltage protector comprises an n-type semiconductor film formed on the marginal portion of the substrate and held against the side surfaces of the light-generating semiconductor region via an insulating film. Creating a pn junction with the marginal portion of the p-type substrate, the n-type semiconductor film provides an overvoltage protector diode which is electrically connected reversely in parallel with the LED. Various other embodiments are disclosed.