Transparent Positive Electrode with Reflecting Layer for GaN Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN-based compound semiconductor light-emitting devices face challenges with current diffusion and light emission due to threading dislocations and high resistivity of p-type layers, leading to limited light extraction and increased drive voltage when using traditional transparent electrodes.
Innovation Solution
A transparent positive electrode with a reflecting layer on the bonding pad electrode is used, ensuring strong adhesion and high reflectance to enhance light extraction efficiency, composed of metals like Al, Ag, or Pt-group metals, and alloys, with specific layer structures and thicknesses to maintain low drive voltage and high emission intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal pad electrode with sufficient thickness is placed on the transparent electrode to establish electric contact, then adhesion and electrical conductivity are improved, but light extraction is reduced due to the electrode's opacity
Solution Approach 1:
The bonding pad electrode is segmented into multiple functional layers: a transparent conductive oxide layer (ITO, IZO, etc.) that allows light extraction, and a separate metal layer (Al, Ag, Au, or their alloys) that provides adhesion and electrical conductivity. This segmentation enables each layer to perform its specialized function without compromising the other.
Solution Approach 2:
The bonding pad electrode uses a composite structure combining transparent conductive oxide materials with metal materials. The transparent conductive oxide layer maintains optical transparency while the metal layer provides mechanical adhesion and electrical conductivity, creating a composite electrode that satisfies multiple requirements simultaneously.
2Reliability
If the p-type GaN-based compound semiconductor layer has high resistivity, then material quality is maintained, but current diffusion is reduced leading to limited light emission area
Solution Approach 1:
The transparent conductive oxide layer acts as an intermediary between the metal pad electrode and the high-resistivity p-type GaN layer. It provides a low-resistivity pathway for current diffusion across the electrode area while maintaining good electrical contact with the semiconductor layer, thereby enabling current to spread laterally without requiring the p-type layer to have low bulk resistivity.
3Reliability
If a stacked layer of Ni and Au is heated in oxygen-containing atmosphere for alloying, then resistance is reduced and Ohmic characteristics are improved, but manufacturing complexity and process temperature requirements increase
Solution Approach 1:
The transparent conductive oxide layer (such as ITO or IZO) is deposited as a thin film that inherently provides both transparency and conductivity. This single-layer or simple multi-layer structure eliminates the need for complex multi-step alloying processes involving Ni/Au stacking and high-temperature oxygen annealing, simplifying the manufacturing process while maintaining electrical performance.
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 allows for intense light emission with reduced drive voltage by minimizing light absorption and maintaining strong adhesion, achieving high emission intensity and efficiency through the use of a reflecting layer on the bonding pad electrode.
Implementation Method 1
a bonding pad electrode formed on the transparent electrode, wherein the bonding pad electrode has a reflecting layer that is in contact with at least the transparent electrode
Data Source
AI summary
An object of the present invention is to provide a transparent positive electrode for use in a face-up-type chip which can emit intense light even using a low drive voltage.The inventive positive electrode for a semiconductor light-emitting device comprises a transparent electrode formed on a semiconductor layer and a bonding pad electrode formed on the transparent electrode, wherein the bonding pad electrode has a reflecting layer that is in contact with at least the transparent electrode.