Nitride Semiconductor Light-Emitting Device Transparent Electrode Layout
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Solution Overview
Problem
Conventional nitride semiconductor light-emitting devices face issues with uneven current distribution and light emission due to concentrated electric currents and voltage, leading to reduced light extraction efficiency and potential electrostatic breakdown, especially when using non-conductive growth substrates and opaque electrodes.
Innovation Solution
A nitride semiconductor light-emitting device is designed with a support substrate, a nitride semiconductor layer, a transparent contact electrode, and a pad electrode positioned to avoid overlap with the active layer's projection region, allowing for improved light extraction efficiency and even current distribution through the use of a transparent electrode and insulating films to prevent current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an opaque pad electrode is used to provide electrical connection, then electrical conductivity is improved, but light extraction efficiency deteriorates due to light absorption
Solution Approach 1:
The electrode structure is segmented into two distinct parts: a transparent conductive oxide layer (ITO) that contacts the active layer and allows light transmission, and a separate opaque pad electrode that provides robust electrical connection. This segmentation resolves the contradiction by assigning different functions to different parts of the electrode system.
Solution Approach 2:
A transparent conductive oxide layer (ITO) is introduced as an intermediary between the active layer and the opaque pad electrode. This intermediary layer provides the necessary electrical conductivity while maintaining optical transparency, thus preventing light absorption and preserving light extraction efficiency.
2Device complexity
If the pad electrode is positioned to overlap with the active layer for direct electrical connection, then electrical connection is simplified, but current distribution becomes uneven leading to electrostatic breakdown
Solution Approach 1:
The transparent conductive oxide layer serves as a mediator that distributes current uniformly across the active layer area without requiring direct contact between the opaque pad electrode and the active layer. This intermediary structure prevents current concentration and electrostatic breakdown while maintaining electrical connection.
Solution Approach 2:
The electrical connection is extended into the vertical dimension by using a transparent conductive oxide layer that can be deposited as a thin film covering the entire active layer area. This dimensional approach allows current to flow uniformly through the transparent layer without concentrating at specific pad locations.
3Loss of energy
If a transparent conductive oxide layer is added between the active layer and pad electrode, then light extraction efficiency is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The transparent conductive oxide layer is designed with specific material parameters (high electrical conductivity and high optical transparency) to achieve the desired performance. By carefully selecting and controlling these parameters, the layer provides both electrical and optical functions without requiring excessive thickness or additional complex structures.
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 enhances light extraction efficiency by preventing light absorption by the pad electrode and ensuring even current distribution, reducing the risk of electrostatic breakdown and improving overall device performance.
Implementation Method 1
a transparent electrode having an optical transparency and formed on the contact electrode
Implementation Method 2
wherein the insulating film is provided between the transparent electrode and the side surface of the nitride semiconductor layer
Data Source
AI summary
A nitride semiconductor light-emitting device includes, a support substrate 170; a nitride semiconductor layer 100 which includes a p-type nitride semiconductor layer 140 formed on the support substrate 170, an MQW active layer 130 formed on the p-type nitride semiconductor layer 140, and an n-type nitride semiconductor layer 120 formed on the MQW active layer 130; a contact electrode 161 formed on the n-type nitride semiconductor layer 120; a second transparent electrode 165 having an optical transparency and formed on the contact electrode 161; and a second pad electrode 166 formed on the support substrate 170 and electrically connected to the second transparent electrode 165, wherein, on a projection plane S parallel to a main surface of the MQW active layer 130, a region on which the MQW active layer 130 is projected and a region on which the second pad electrode 166 is projected are not overlapped.