Nitride Semiconductor Light Emitting Device Electron Blocking Layer
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Solution Overview
Problem
Nitride semiconductor light emitting devices experience a decrease in light emission efficiency due to electron leakage current at high currents, primarily caused by net polarization mismatch between quantum barrier and electron blocking layers, which current technologies have not effectively addressed.
Innovation Solution
A nitride semiconductor light emitting device is designed with an electron blocking layer having a superlattice structure with alternating layers of different compositions, where the net polarization mismatch between the electron blocking layer and adjacent quantum barrier layers is minimized, typically less than two-thirds of the mismatch between AlxG1-xN and adjacent layers, to reduce electron leakage and enhance light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional electron blocking layer structure is used, then device structure is simple, but electron leakage current increases at high currents
Solution Approach 1:
The electron blocking layer is divided into multiple sub-layers with different compositions and thicknesses. Specifically, it includes a first electron blocking layer with Al content of 0.05-0.20 and thickness of 5-15 nm, and a second electron blocking layer with Al content of 0.20-0.35 and thickness of 15-30 nm. This segmentation allows each sub-layer to perform specific functions in reducing electron leakage at different energy levels.
Solution Approach 2:
Different regions of the electron blocking layer are assigned different material compositions and thicknesses to optimize local electron blocking performance. The first electron blocking layer uses lower Al content for moderate blocking, while the second electron blocking layer uses higher Al content for stronger blocking, creating a gradient structure that effectively addresses electron leakage throughout the layer.
2Loss of energy
If higher Al content is used in electron blocking layer, then electron leakage is reduced, but quantum efficiency decreases
Solution Approach 1:
The electron blocking function is segmented across two layers with different Al contents. The first layer (lower Al) maintains good electron transport and recombination characteristics for high quantum efficiency, while the second layer (higher Al) provides strong electron blocking to reduce leakage current, thus achieving both goals simultaneously.
Solution Approach 2:
The Al content parameter is changed progressively from the first to the second electron blocking layer. This gradual parameter change allows the structure to transition from a region favoring electron injection and recombination to a region favoring electron blocking, optimizing both quantum efficiency and leakage reduction.
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
The solution significantly reduces electron leakage current and improves light emission efficiency, maintaining high quantum efficiency even at high currents, thereby addressing the limitations of existing nitride semiconductor light emitting devices.
Implementation Method 1
an absolute value of a net polarization mismatch between a material, the material having a composition corresponding to an average composition of the superlattice structure, and a quantum barrier layer adjacent to the electron blocking layer among the plurality of quantum barrier layers is less than two thirds (2/3) of an absolute value of a net polarization mismatch between AlxG1-xN (0
Data Source
AI summary
A nitride semiconductor light emitting device includes n-type and p-type nitride semiconductor layers; an active layer disposed between the n-type and p-type nitride semiconductor layers and having a structure in which a plurality of quantum barrier layers and one or more quantum well layers are alternately stacked; and an electron blocking layer disposed between the active layer and the p-type nitride semiconductor layer. The electron blocking layer has a superlattice structure in which two or more layers having different compositions are alternately stacked. An absolute value of a net polarization mismatch between a material, the material having a composition corresponding to an average composition of the superlattice structure, and a quantum barrier layer adjacent to the electron blocking layer among the plurality of quantum barrier layers is less than ⅔ of an absolute value of a net polarization mismatch between AlxG1-xN(0<x<1) having bandgap energy equal to that of the material and a composition different thereto and the adjacent quantum barrier layer.