Quantum Well LED Structure for UV Output and Carrier Confinement
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Solution Overview
Problem
Current light-emitting diode (LED) technology, particularly nitride-based laser diodes for 3D printing, is limited by poor crystalline quality of epitaxial layers due to the lack of a suitable substrate that matches GaN in both lattice parameters and thermal expansion coefficient.
Innovation Solution
A light-emitting device is designed with a substrate, a base layer of Al(x)Ga(1-x)N, and a diode layer structure comprising a quantum well layer structure sandwiched between n-doped and p-doped semiconductor layers. The quantum well layer structure includes proximal and distal barrier layers to enhance carrier injection and confinement, improving crystalline quality and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional substrate materials are used for GaN-based light-emitting devices, then manufacturing is easier and cost is lower, but crystalline quality deteriorates due to lattice mismatch and thermal expansion differences
Solution Approach 1:
The patent introduces an AlN base layer as an intermediary between the substrate and the GaN quantum well structure. This base layer serves as a buffer that compensates for lattice mismatch and thermal expansion differences, thereby improving crystalline quality without requiring a perfect lattice-matched substrate. The AlN layer has a smaller lattice constant than GaN, making it suitable as a buffer layer on conventional substrates like silicon or sapphire.
2Power
If single quantum well structures are used, then device structure is simpler, but light-emission efficiency and output power are limited
Solution Approach 1:
The patent employs multiple quantum well layers (first and second quantum wells) with different bandgaps arranged in sequence within the diode layer structure. Each quantum well contributes to light emission at different wavelengths, and their combined effect increases overall output power and efficiency. The segmented structure allows for broader spectral coverage and higher total optical output compared to a single quantum well.
3Reliability
If conventional barrier layers are used in quantum well structures, then manufacturing is simpler, but carrier confinement and injection efficiency deteriorate
Solution Approach 1:
The patent introduces proximal barrier layers with specific doping characteristics (intrinsically doped or compensated) positioned immediately adjacent to the quantum wells, and distal barrier layers with different aluminum content further away. The proximal barrier layers provide strong carrier confinement to the quantum wells while the distal barrier layers provide additional confinement and protect against dopant diffusion. This localized differentiation of barrier layer properties optimizes carrier injection and confinement efficiency.
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 proposed device achieves high output power and improved crystalline quality of the quantum wells, leading to enhanced light-emission efficiency and the ability to emit ultraviolet (UV) light, which addresses the limitations of current nitride-based laser diodes.
Implementation Method 1
the n-doped semiconductor layer is configured to inject electrons into the quantum well layer structure
Implementation Method 2
the p-doped semiconductor layer is configured to inject holes into the quantum well layer structure
Implementation Method 3
Electrons and holes injected into the quantum well layer structure recombine in the first and second quantum well of the quantum well layer structure whereby the device emits light
Implementation Method 4
the first and second quantum well each has a thickness below 5 nm and a bandgap smaller than bandgaps of the first and second proximal barrier layers
Data Source
AI summary
A device (1) for emitting light, the device (1) comprising: a substrate (2); abase layer (4) arranged on the substrate (2); a diode layer structure (10) arranged on the base layer (4), the diode layer structure (10) comprising a quantum well layer structure (30) sandwiched between an n-doped semiconductor layer (12) and a p-doped semiconductor layer (14); the quantum well layer structure (30) comprising a first (41) and second (42) quantum well, a first (51) and a second (52) proximal barrier layer, and a first (61) and a second (62) distal barrier layer, wherein the first (41) and second (42) quantum wells and the first (51) and second (52) proximal barrier layers are sandwiched between the first (61) and second (62) distal barrier layers