Transparent Nitride Contact Layer for Low-Resistance LED Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor-based light emitting devices face challenges in achieving high conversion efficiency, high-intensity light emission, homogeneous current spreading, low contact resistances, and high transparency due to the complexities of Mg-doped III-nitride layers and difficulties in controlling metallic or semi-transparent conductive contacts.
Innovation Solution
The implementation of a transparent conductive nitride layer (TCN) with low resistivity, deposited directly on a first layer using Molecular Beam Epitaxy (MBE) to overcome the limitations of Mg-doped III-nitride layers, ensuring excellent crystallinity and transparency, and the use of a current aperture stop for precise current confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Mg-doped III-nitride layers are used for light emission, then light emission is achieved, but high resistivity and low hole concentrations occur
Solution Approach 1:
An undoped or lightly-doped III-nitride intermediate layer is introduced between the Mg-doped contact layer and the active region. This intermediate layer acts as a mediator that improves hole transport and reduces contact resistance without interfering with the light emission properties of the Mg-doped layer, thereby resolving the contradiction between achieving light emission and maintaining low resistivity.
Solution Approach 2:
Different doping strategies are applied to different regions: the contact layer uses Mg doping for hole injection, while the intermediate layer uses undoped or lightly-doped structure for optimized transport. This local differentiation allows each region to perform its specific function optimally, reducing overall resistivity while maintaining light emission capability.
2Illumination intensity
If Mg-doped III-nitride layers are used, then light emission is achieved, but control of metallic or semitransparent conductive contacts becomes difficult
Solution Approach 1:
The undoped or lightly-doped intermediate layer serves as an intermediary between the Mg-doped contact layer and the metallic contact, providing a buffer zone that facilitates better control of contact properties. This intermediate layer enables more predictable and controllable formation of metallic or semitransparent contacts while preserving the light emission characteristics of the underlying Mg-doped structure.
3Illumination intensity
If Mg-doped III-nitride layers are used, then light emission is achieved, but conversion efficiency is limited due to low hole mobility
Solution Approach 1:
The undoped or lightly-doped intermediate layer acts as a mediator that facilitates more efficient hole transport from the Mg-doped contact layer to the active region. By providing a low-resistivity pathway with reduced scattering, this intermediate layer improves hole mobility and thereby enhances the overall conversion efficiency of electrical energy to light emission.
Solution Approach 2:
The doping concentration parameter is changed in the intermediate layer (reduced from heavily Mg-doped to undoped or lightly-doped), which optimizes the balance between hole injection and hole transport. This parameter change reduces resistivity and improves hole mobility, leading to better conversion efficiency while maintaining light emission.
4Reliability
If transparent layer with high conductivity is added, then contact resistance is reduced, but device structure becomes more complex
Solution Approach 1:
The intermediate layer is made of the same or similar III-nitride material as the surrounding layers, ensuring homogeneous crystal structure and lattice matching. This material homogeneity reduces interface defects and dislocations, allowing the addition of the intermediate layer to increase contact resistance performance without proportionally increasing device complexity.
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 results in devices with significantly reduced contact resistances, enhanced current spreading, and improved light emission efficiency, achieving low resistivities and high transparency, particularly suitable for top-emitting devices like VCSELs.
Implementation Method 1
The transparent layer can have a low resistivity. The transparent layer can have a resistivity so low that it can be considered an electrically conductive layer.
Implementation Method 2
a transparent layer of a nitride of one or more group-III elements, which is transparent to light emitted from the semiconductor structure
Implementation Method 3
is epitaxially grown to minimize interface resistances and defects
Data Source
Figure 1~3
Figure 4~6
Figure 7~10
AI summary
The device can be a light emitting device such as an LED or a laser and 5comprises - a semiconductor structure operable to emit light and comprising a first layer and a second layer; and in addition, - a transparent layer of a nitride of one or more group-III elements, which is transparent to light emitted from the semiconductor structure. The transparent layer is present on the first layer and has an electrical conductivity exceeding an electrical conductivity of the first layer. The semiconductor structure can be epitaxial with the transparent layer. A current aperture can be provided which is epitaxial with both, the transparent layer and the first layer. The first layer can be an Mg-doped nitride of one or more group-III elements.