High Current Density LED with Bulk Substrate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED devices face limitations in achieving high current density due to efficiency 'droop' and reliability issues, which restrict cost reduction and energy savings, as they require larger semiconductor areas and suffer from thermal and current crowding problems.
Innovation Solution
High current density LED devices are fabricated using bulk gallium and nitrogen-containing substrates with polar, semipolar, or nonpolar orientations, enabling increased active area utilization and maintaining high external quantum efficiency, with current densities exceeding 175 A/cm2 and internal quantum efficiency of at least 50%, and featuring reduced dislocation densities for enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current density is increased to reduce cost and increase lumens per unit area, then productivity and cost-effectiveness improve, but efficiency droop occurs and internal quantum efficiency decreases
Solution Approach 1:
The patent changes the operational parameters by operating the LED at high current densities (greater than 175 A/cm²) that were previously avoided due to efficiency droop. This is made possible by changing the physical structure (bulk substrate with reduced dislocation density) which allows the parameter change without suffering from the traditional efficiency loss.
Solution Approach 2:
The patent extracts the limiting factor (dislocation density) by using bulk gallium nitride substrates with reduced dislocation densities. By removing this defect source, the LED can operate at high current densities without the efficiency droop that plagues conventional LEDs grown on foreign substrates.
2Area of stationary object
If current density is increased to reduce semiconductor material area, then area usage improves, but thermal gradients and current crowding cause reliability issues
Solution Approach 1:
The patent changes the thermal and electrical parameters by operating at high current densities with improved heat dissipation and current distribution. The bulk substrate provides better thermal management, allowing high current operation without the reliability-degrading thermal gradients and current crowding effects.
Solution Approach 2:
The patent extracts the thermal and electrical management problems by using bulk substrates that provide superior thermal conduction and more uniform current distribution, eliminating the thermal gradients and current crowding that occur in conventional thin-film or foreign-substrate LEDs.
3Ease of manufacture
If conventional foreign substrate methods are used, then manufacturing is easier, but dislocation density increases and reduces efficiency
Solution Approach 1:
The patent changes the material parameter from foreign substrates to bulk gallium nitride substrates. This material change reduces dislocation density and improves internal quantum efficiency, while the patent acknowledges that the manufacturing process becomes more challenging, representing a trade-off that prioritizes performance over ease of manufacture.
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 approach allows for higher yields and reduced costs by minimizing semiconductor material usage while maintaining high efficiency and reliability, enabling the production of LEDs with increased lumens per unit area and extended operational lifetimes.
Implementation Method 1
one or more active regions formed overlying the surface region, with a current density of greater than about 175 Amps/cm2 characterizing the one or more active regions
Data Source
AI summary
A light emitting diode device emitting at a wavelength of 390-415 nm has a bulk gallium and nitrogen containing substrate with an active region. The device has a current density of greater than about 175 Amps/cm2 and an external quantum efficiency with a roll off of less than about 5% absolute efficiency.