Beryllium-Doped GaN LED p-Type Activation for Lower Resistivity
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Solution Overview
Problem
GaN-based LEDs suffer from high resistivity p-type regions, which limits their efficiency due to deep binding energy and passivation with atomic hydrogen, making it difficult to achieve low resistivity p-type materials using traditional dopants like magnesium.
Innovation Solution
Incorporating beryllium as a p-type dopant in GaN-based materials through ion implantation and a three-step annealing process, including a high-temperature pulsed laser anneal, to activate beryllium atoms and reduce resistivity, thereby increasing hole concentration and improving electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional dopants like magnesium are used in GaN-based LEDs, then the doping process is simpler, but the resistivity of p-type regions remains high due to deep binding energy and passivation with atomic hydrogen
Solution Approach 1:
The patent changes the dopant parameter from traditional magnesium to beryllium, which has shallower binding energy in GaN. This parameter change enables higher hole concentrations and lower resistivity in p-type regions, directly resolving the electrical conductivity issue while maintaining process compatibility
Solution Approach 2:
The patent replaces the conventional thermal annealing process with pulsed laser annealing. This substitution uses localized optical energy to activate beryllium dopants without causing excessive hydrogen incorporation, thereby achieving low resistivity while avoiding the passivation problem that plagues traditional methods
2Reliability
If high temperature annealing is performed to activate dopants, then hole concentration increases, but efficiency droop increases due to excessive hydrogen incorporation
Solution Approach 1:
The patent replaces conventional thermal annealing with pulsed laser annealing. The laser provides localized, rapid heating that activates beryllium dopants effectively while minimizing the time for hydrogen diffusion and incorporation. This resolves the contradiction by achieving high hole concentration without the penalty of excessive hydrogen-related efficiency droop
Solution Approach 2:
The pulsed laser annealing uses periodic, ultra-short duration pulses rather than continuous heating. This periodic action delivers the necessary thermal energy to activate dopants while allowing the material to cool rapidly between pulses, preventing excessive hydrogen incorporation that would cause efficiency droop
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 use of beryllium as a p-type dopant results in higher hole concentrations, leading to lower operating voltages, increased emission intensity, and reduced efficiency droop, potentially improving LED efficiency by up to 20% compared to traditional magnesium-doped LEDs.
Implementation Method 1
subjecting the region of the semiconductor substrate using a pulsed laser to achieve a surface temperature greater than 1000 degrees Celsius for a time period of shorter than one second
Implementation Method 2
introducing a plurality of impurities into a region of the semiconductor substrate using an ion implantation process
Implementation Method 3
performing an isothermal anneal on the region of the semiconductor substrate in a hydrogen and ammonia free ambient at temperatures in the range from 700 to 900 degrees Celsius for time period of greater than one second to facilitate removal of atomic hydrogen entities
Data Source
AI summary
The invention described herein provides a method and apparatus to realize incorporation of Beryllium followed by activation to realize p-type materials of lower resistivity than is possible with Magnesium. Lower contact resistances and more effective electron confinement results from the higher hole concentrations made possible with this invention. The result is a higher efficiency GaN-based LED with higher current handling capability resulting in a brighter device of the same area.