N-P-N Nitride Semiconductor Light-Emitting Device Current Confinement
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Solution Overview
Problem
Conventional nitride semiconductor light-emitting devices with current confinement structures using buried tunnel junctions face issues with luminous efficacy due to leakage currents, as thermal annealing activates p-type GaN crystals beyond the intended current confinement region, leading to increased resistance and reduced light emission efficiency.
Innovation Solution
A method involving two-stage thermal annealing is employed to selectively control hydrogen atom distribution in the p-type GaN crystal layer, activating Mg atoms as acceptors only in the current confinement region while deactivating them in other areas, thereby confining the current and reducing leakage, and the buried tunnel junction is used to form a low-resistance path within the confinement region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal annealing is performed to activate p-type GaN crystals, then conductivity is improved, but current confinement is degraded due to activation beyond the intended region
Solution Approach 1:
The patent applies local quality by creating distinct regions within the p-type GaN layer: a first region under the positive electrode with high conductivity (activated), a second region at the periphery with low conductivity (deactivated), and a third region between them with controlled conductivity. This spatial variation in electrical properties enables both overall conductivity improvement and precise current confinement, resolving the contradiction between these two requirements.
2Reliability
If a buried tunnel junction is used to form a low-resistance path, then current confinement is improved, but leakage currents increase due to activation in unintended regions
Solution Approach 1:
The patent implements local quality by spatially differentiating the electrical activation state across the p-type GaN layer. The first region directly under the positive electrode is activated to provide low resistance for the desired current path through the tunnel junction. The second peripheral region remains deactivated to block leakage currents. This localized control of conductivity resolves the contradiction between achieving good current confinement and preventing energy loss through leakage.
3Reliability
If Mg atoms are activated as acceptors throughout the p-type GaN layer, then conductivity increases, but resistance in non-confinement regions decreases leading to current spread
Solution Approach 1:
The patent applies local quality by selectively activating Mg atoms as acceptors only in specific regions. The first region under the positive electrode has activated Mg atoms providing high conductivity for the intended current path. The second peripheral region has deactivated Mg atoms maintaining high resistance to prevent current spread. This spatially selective activation resolves the contradiction between achieving sufficient conductivity and maintaining precise current path control.
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
This approach effectively confines the current within the intended region, enhancing luminous efficacy by minimizing leakage currents and maintaining low resistance in the active p-type GaN crystal layer, while maintaining high resistance in regions outside the confinement area, resulting in improved light output even at lower current densities.
Implementation Method 1
The activation of the p-type nitride semiconductor is performed by thermal annealing. Generally, a p-type GaN crystal used as a p-type nitride semiconductor is configured using, for example, Mg atoms or the like as acceptor impurities. Hydrogen atoms produced in a manufacturing process has the property of being taken into the crystal and easily combined with Mg atoms. If Mg atoms are combined with hydrogen atoms, Mg atoms are deactivated and may not function as acceptors. As a result, the GaN crystal may not behave as p-type to lose conductivity and may come to have high resistance. Thermal annealing breaks bonds between hydrogen atoms and Mg atoms and allows hydrogen atoms to exit to the outside of the crystal. This activates Mg atoms as acceptors, and a p-type GaN crystal having conductivity can be obtained.
Implementation Method 2
A tunnel junction is a junction relating to a tunnel diode having negative resistance characteristics, which is known as a so-called Esaki diode or the like. With the tunnel junction, unlike rectifying characteristics exhibited by general diodes, a current can be reversely passed from an n layer to a p layer, current-voltage characteristics thereof are ohmic like. For the utilization of the ohmic characteristics in the reverse direction, a tunnel junction having an n-type semiconductor layer on a positive electrode side and a p-type semiconductor layer on a negative electrode side is disposed in a current path inside the ring of the positive electrode. A current is concentrated at the tunnel junction and flows by the tunnel effect.
Data Source
AI summary
This application provides a method of manufacturing an n-p-n nitride-semiconductor light-emitting device which includes a current confinement region (A) using a buried tunnel junction layer and in which a favorable luminous efficacy can be obtained and to provide the n-p-n nitride-semiconductor light-emitting device. The p-type activation of a p-type GaN crystal layer stacked below a tunnel junction layer is performed in an intermediate phase of a manufacturing process in which the p-type GaN crystal layer is exposed to atmosphere gas with the tunnel junction layer partially removed, before the tunnel junction layer is buried in an n-type GaN crystal layer. In the intermediate phase of the manufacturing process in which the p-type GaN crystal layer is exposed, p-type activation is efficiently performed on the p-type GaN crystal layer, and a p-type GaN crystal layer with low electric resistance can be obtained.