Light Emitting Device Current Reducing Structures
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Solution Overview
Problem
Conventional semiconductor light emitting devices, such as LEDs, suffer from reduced efficiency due to light absorption by non-transparent wire bond pads, which prevents photons from escaping and decreases the overall light emission.
Innovation Solution
A light emitting device design incorporating a reduced conductivity region aligned with the wire bond pad to block current flow beneath it, preventing light absorption and enhancing photon emission by redirecting carrier injection to areas outside the wire bond pad.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wire bond pad is used for electrical connection, then electrical connectivity is achieved, but light absorption increases and light extraction efficiency decreases
Solution Approach 1:
The device structure is segmented into distinct functional zones: a current blocking region beneath the wire bond pad that prevents carrier injection, and current spreading regions in surrounding areas that facilitate carrier flow. This segmentation ensures current is directed away from light-absorbing areas while maintaining electrical connectivity through the bond pad.
Solution Approach 2:
Different regions of the semiconductor device are assigned different electrical properties: the region beneath the wire bond pad has reduced conductivity to block current, while surrounding regions maintain normal or enhanced conductivity for current spreading. This local differentiation optimizes both electrical connectivity and light extraction in specific zones.
2Reliability
If current spreading layer is used to improve carrier injection uniformity, then carrier distribution improves, but light absorption by bond pad increases
Solution Approach 1:
A current blocking structure is placed beneath the wire bond pad to preemptively prevent carrier injection in the region where light absorption would occur. This preliminary action stops carriers from reaching the bond pad area before they can generate light that would be absorbed, thereby counteracting the harmful effect in advance.
Solution Approach 2:
The wire bond pad, which inherently absorbs light and reduces efficiency, is positioned over a current blocking region. This converts the potentially harmful light-absorbing structure into a beneficial configuration where the bond pad serves its electrical function without causing significant light loss, as no light is generated in the blocked region beneath it.
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 design increases the efficiency of light emitting devices by reducing light absorption at the wire bond pad, leading to improved light extraction and enhanced performance, particularly suited for nitride-based LEDs.
Implementation Method 1
a reduced conductivity region in the p-type semiconductor layer and is aligned with the wire bond pad. The reduced conductivity region extends from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region
Implementation Method 2
a semiconductor light emitting device includes a semiconductor light emitting element having one or more semiconductor layers that are configured to emit coherent and/or incoherent light upon energization thereof
Implementation Method 3
Light generated in an active region of the device is proportional to the carrier injection
Implementation Method 4
a wire bond pad is typically not a transparent structure and, therefore, photons emitted from the active region of the LED that are incident upon the wire bond pad may be absorbed by the wire bond pad. For example, in some instances approximately 70% of the light incident on the wire bond pad may be absorbed
Data Source
Figure 1~2A
Figure 2B~3
Figure 4A~4B
AI summary
A light emitting device includes a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer. A non-transparent feature, such as a wire bond pad, is on the p-type semiconductor layer or on the n-type semiconductor layer opposite the p-type semiconductor layer, and a reduced conductivity region is in the p-type semiconductor layer or the n-type semiconductor layer and is aligned with the non-transparent feature. The reduced conductivity region may extend from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region and/or from a surface of the n-type semiconductor layer opposite the p-type semiconductor layer towards the active region.