Multiple-Well GaN Light Emitting Device for Efficiency
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Solution Overview
Problem
Nitride semiconductor light emitting devices face reduced light emission efficiency due to lower hole mobility and activated hole concentration, leading to degraded luminous intensity and optical characteristics, especially under high current conditions.
Innovation Solution
A light emitting device structure with a multiple-well layer active layer, including a first well layer, a second well layer with a higher energy bandgap, and a third well layer, where the third well layer is grown at a higher temperature to increase its energy bandgap and enhance hole injection efficiency, while maintaining uniform carrier distribution across the active layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-well layer active layer is used, then the device structure is simple, but the luminous intensity is reduced due to low hole mobility and concentrated carrier distribution
Solution Approach 1:
The active layer is segmented into multiple well layers (first, second, and third well layers) with different energy bandgaps, allowing carriers to be distributed across multiple regions rather than concentrated in a single well layer. This segmentation enables multiple recombination zones that contribute to higher overall luminous intensity while managing carrier distribution effectively.
Solution Approach 2:
Each well layer is assigned a specific energy bandgap value tailored to its position and function: the first well layer has a lower energy bandgap, the second well layer has a higher energy bandgap, and the third well layer has an intermediate energy bandgap. This local quality differentiation optimizes carrier injection and recombination at each location, improving overall light emission efficiency.
2Reliability
If the third well layer is grown at a higher temperature to increase energy bandgap, then hole injection efficiency is enhanced, but the manufacturing process complexity increases
Solution Approach 1:
The growth temperature parameter is changed for the third well layer compared to the first and second well layers. Specifically, the third well layer is grown at a higher temperature to achieve a higher energy bandgap, which improves hole injection efficiency. This parameter change is deliberately applied to optimize the electrical and optical characteristics of the active layer.
3Productivity
If carriers are concentrated in the well layer adjacent to the P-type GaN layer, then light emission occurs primarily from that region, but the overall light emission efficiency is reduced
Solution Approach 1:
The active layer is divided into multiple well layers that serve as separate recombination regions. Instead of concentrating carriers in a single well layer adjacent to the P-type GaN layer, the segmented structure distributes carriers across multiple well layers, enabling multiple sites for radiative recombination and thereby improving overall light emission efficiency.
Solution Approach 2:
Different well layers are designed with different energy bandgaps to create localized regions with optimized carrier confinement and recombination characteristics. The first well layer has a lower energy bandgap, the second well layer has a higher energy bandgap, and the third well layer has an intermediate energy bandgap, creating a gradient that improves carrier distribution and reduces energy loss.
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 configuration improves luminous intensity and light emission efficiency by increasing carrier injection and recombination rates, reducing the droop phenomenon, and minimizing wavelength variation, thereby enhancing the reliability and optical characteristics of the light emitting device.
Implementation Method 1
the forming of the second well layer is performed at a third growth temperature, the forming of the third well layer is performed at a fourth growth temperature, and the fourth growth temperature is higher than the third growth temperature
Implementation Method 2
when a forward voltage is applied, electrons injected from an N-type GaN based electron injection layer are combined with holes injected from a P-type GaN based hole injection layer, so that energy corresponding to the energy gap between a conduction band and a valance band is radiated. The energy is mainly emitted in the form of heat or light.
Data Source
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Figure 3~4
Figure 5A~5C
AI summary
Disclosed are a light emitting device, a method for manufacturing the same, a light emitting device package, and a lighting system. The light emitting device includes a first conductive semiconductor layer, an active layer comprising a well layer and a barrier layer on the first conductive layer, and a second conductive semiconductor layer on the active layer. The well layer includes a first well layer closest to the first conductive semiconductor layer and having a first energy bandgap, a third well layer closest to the second conductive semiconductor layer and having a third energy bandgap, and a second well layer interposed between the first and third well layers and having a second energy bandgap. The third energy bandgap of the third well layer is greater than the second energy bandgap of the second well layer.