Nonpolar GaN Light Emitting Device with Polar Contact Segmentation
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Solution Overview
Problem
Achieving excellent ohmic contact with n-type electrodes on group III nitride semiconductor devices with nonpolar surfaces is challenging due to random polarization of light emitted from c-plane surfaces, leading to reduced brightness and efficiency in liquid crystal displays.
Innovation Solution
The semiconductor light emitting device incorporates a contact portion with a crystal plane different from the major surface, such as a polar or semipolar plane, to form excellent ohmic contact with the n-type electrode, and uses a corrugated surface structure to increase the contact area, thereby improving the ohmic contact and reducing polarization-related losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a GaN semiconductor layer with a nonpolar plane major surface is used, then strongly polarized light can be emitted, but excellent ohmic contact with n-type electrode cannot be achieved
Solution Approach 1:
The device is divided into two distinct functional regions: a nonpolar plane major surface for light emission and a polar plane contact portion for electrical contact. This segmentation allows each region to optimize its specific function without compromising the other.
Solution Approach 2:
Different crystal plane orientations are assigned to different locations of the semiconductor layer. The major surface maintains a nonpolar plane orientation for polarization performance, while the contact portion has a polar plane orientation for electrical contact performance. This local differentiation resolves the contradiction between optical and electrical requirements.
2Ease of manufacture
If a c-plane GaN semiconductor is used, then manufacturing is easier, but light polarization is random leading to reduced display efficiency
Solution Approach 1:
The crystal plane orientation parameter is changed from c-plane to nonpolar plane (a-plane or m-plane) for the major surface to achieve strong light polarization. This parameter change improves display brightness by enabling polarization matching with liquid crystal panels while maintaining manufacturing feasibility through established growth techniques.
Data Source
AI summary
A semiconductor light emitting device has a device body made of a group III nitride semiconductor having a major surface defined by a nonpolar plane. In the device body, a contact portion with an n-type electrode includes a crystal plane different from the major surface. For example, the contact portion may include a corrugated surface. More specifically, the contact portion may include a region having a plurality of protrusions parallel to a polar plane formed in a striped manner.