UV LED p-GaN Contact Layer Segmentation
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Solution Overview
Problem
The production of ultraviolet light emitting diodes (UV LEDs) faces challenges in achieving high light coupling-out efficiency due to the absorption of radiation by continuous p-GaN layers, which reduces the external quantum efficiency and electrical efficiency.
Innovation Solution
The method involves growing a p-type semiconductor contact layer with varying thickness and multiple thickness maxima on the p-layer, forming three-dimensional structures that increase the extraction probability of ultraviolet radiation, and applying an ohmic-conductive electrode layer to enhance reflectivity and current injection, while maintaining a reduced p contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous p-GaN layer is used, then good electrical contact is achieved, but light absorption increases and external quantum efficiency decreases
Solution Approach 1:
The continuous p-GaN contact layer is segmented into discrete contact regions with varying thickness. The contact layer consists of multiple thickness maxima distributed across the surface, creating isolated contact zones rather than a continuous absorbing layer. This segmentation reduces the total volume of absorbing material while maintaining electrical contact functionality.
Solution Approach 2:
The contact layer exhibits spatially varying thickness with localized maxima and minima. Regions with thickness maxima provide enhanced electrical contact and current injection, while regions with minimal thickness reduce light absorption. This local variation in thickness allows different areas to serve different functions - electrical contact versus light transmission.
2Loss of energy
If the p contact area is reduced to decrease absorption, then external quantum efficiency increases, but electrical contact quality may deteriorate
Solution Approach 1:
The thickness parameter of the contact layer is varied spatially to optimize both electrical and optical performance. By controlling the thickness distribution with multiple maxima of different heights and positions, the contact layer achieves reduced overall absorption while maintaining sufficient contact area for electrical function. The thickness parameter is the key variable that reconciles the contradiction between contact area and absorption.
Solution Approach 2:
The contact layer structure transitions from a two-dimensional continuous plane to a three-dimensional structured surface with varying thickness. This dimensional complexity allows the contact layer to provide electrical contact through protruding regions while minimizing absorption through recessed areas, effectively using the thickness dimension to resolve the area-absorption trade-off.
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 significantly increases the external quantum efficiency of UV LEDs by more than a factor of 2, compensating for the reduced p contact area and enhancing the overall efficiency of light emission.
Implementation Method 1
an active zone (23) arranged between them and configured to generate ultraviolet radiation
Implementation Method 2
The semiconductor contact layer (25) has a varying thickness and has a plurality of thickness maxima (4). This approach significantly increases the external quantum efficiency of UV LEDs by more than a factor of 2
Implementation Method 3
An ohmic-conductive electrode layer (3) is applied directly to the semiconductor contact layer (25). The electrode layer preferably contains one or more metal layers
Data Source
AI summary
In an embodiment a light emitting diode includes an n-type n-layer, a p-type p-layer and an intermediate active zone configured to generate ultraviolet radiation, a p-type semiconductor contact layer having a varying thickness and a plurality of thickness maxima directly located on the p-layer and an ohmic-conductive electrode layer directly located on the semiconductor contact layer, wherein the n-layer and the active zone are each of AlGaN and the p-layer is of AlGaN or InGaN, wherein the semiconductor contact layer is a highly doped GaN layer, and wherein the thickness maxima have an area concentration of at least 104 cm−2.