Nitride Semiconductor Light-Emitting Device V-Pit Dislocation Management
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Solution Overview
Problem
Nitride semiconductor light-emitting devices suffer from poor electrostatic discharge (ESD) characteristics due to crystal defects, particularly threading dislocations, which lead to current leakage and reduced reliability, especially under reverse voltage conditions, limiting their application in harsh environments.
Innovation Solution
A nitride semiconductor light-emitting device with a V-shaped (v-pit) structure at specific junction surfaces and a high-resistance semiconductor layer with controlled impurity concentration and thickness, combined with a method of flattening v-pit structures to minimize current leakage and enhance durability, thereby improving reverse voltage characteristics and uniform luminosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a v-pit structure is formed on the active layer to increase barrier height and reduce non-radiative recombination, then internal quantum efficiency is improved, but optical output decreases due to reduced light-emitting region
Solution Approach 1:
The patent applies local quality by forming v-pit structures only in specific regions (n-type cladding layer and p-type cladding layer) while keeping the active layer plane, rather than forming v-pits throughout the entire device. This localized approach allows barrier height enhancement and non-radiative recombination reduction in the cladding regions without sacrificing the light-emitting area of the active layer, thus resolving the contradiction between improved internal quantum efficiency and maintained optical output
2Ease of manufacture
If crystal defects (threading dislocations) are present in the GaN layer, then device manufacturing is simplified, but current leakage increases and electrostatic discharge characteristics deteriorate
Solution Approach 1:
The patent extracts or removes the harmful effect of threading dislocations by forming v-pit structures that trap and isolate dislocations away from the active layer. The v-pits act as dislocation sinks, preventing dislocations from propagating into the active region, thereby reducing current leakage and improving ESD characteristics while maintaining the simplicity of GaN layer growth
Solution Approach 2:
The v-pit structures serve as intermediary elements between the substrate and the active layer. They provide a transition zone that manages dislocation propagation, allowing the device to benefit from simple GaN growth while the v-pits mediate the harmful effects of crystal defects before they reach the active region
3Device complexity
If N-electrode and P-electrode are formed at the same plane to simplify device structure, then device complexity is reduced, but current concentration around N-electrode intensifies and ESD characteristics worsen
Solution Approach 1:
The patent applies dimensionality change by introducing vertical depth variation through v-pit structures in the cladding layers, while maintaining the planar electrode configuration. The v-pits create additional vertical space and current path distribution without requiring complex three-dimensional electrode structures, thus reducing current concentration and improving ESD characteristics while keeping the device structure relatively simple
Data Source
AI summary
A nitride semiconductor light-emitting device comprises a substrate; a first conductivity type semiconductor layer formed on the substrate; a high-resistance semiconductor layer formed on the first conductivity type semiconductor layer; an active layer formed on the high-resistance semiconductor layer and having multiple quantum wells; and a second conductivity type semiconductor layer formed on the active layer. A first v-pit structure is formed between the high-resistance semiconductor layer and the first conductivity type semiconductor layer, and a second v-pit structure is formed between the active layer and the second conductivity type semiconductor layer. The second v-pit structure is formed such that a lowest part of the second conductivity type semiconductor layer contacts a lowest quantum well of the multiple quantum wells of the active layer through the second v-pit structure.