GaN Light Emitting Device Electron Barrier Layer Optimization
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Solution Overview
Problem
Semiconductor lasers using nitride III-V compound semiconductors face reduced luminance efficiency due to electron overflow and crystal defects in the electron barrier layer, which also impede hole injection and cause light absorption by p-type dopants like Mg.
Innovation Solution
A semiconductor light emitting device with a gallium nitride compound semiconductor structure, featuring a first cladding layer, an active layer, an electron barrier layer made of InxAlyGa1-x-yN with a larger band gap, and a second cladding layer, where the electron barrier layer's thickness is between 2 nm and 7 nm, and optionally includes an InGaN intermediate layer to enhance the effective barrier height and reduce strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Al composition ratio of AlGaN or AlInGaN electron barrier layer is increased to suppress electron overflow, then the barrier effect against electrons is improved, but crystal defects are generated and luminance efficiency is reduced
Solution Approach 1:
The patent changes the thickness parameter of the electron barrier layer from conventional thick designs to a specific range of 2-7 nm. This parameter change allows the layer to maintain electron barrier function while reducing the accumulation of crystal defects that occur with higher Al composition ratios, thereby resolving the contradiction between electron overflow suppression and crystal quality
Solution Approach 2:
The patent uses a composite structure combining InGaN intermediate layer with AlGaN electron barrier layer. The InGaN layer with smaller lattice constant helps reduce strain and crystal defects in the AlGaN layer, allowing the barrier layer to maintain high electron suppression capability without generating excessive crystal defects
2Reliability
If the electron barrier layer has a larger band gap to suppress electron overflow, then electron suppression is improved, but hole injection into the active layer is impeded
Solution Approach 1:
The patent optimizes the thickness parameter of the electron barrier layer to 2-7 nm, which is thin enough to allow hole tunneling through the large band gap material, while still maintaining sufficient electron barrier height. This resolves the contradiction by enabling holes to pass through via quantum tunneling effect despite the large band gap
Solution Approach 2:
The patent introduces an InGaN intermediate layer between the active layer and the AlGaN electron barrier layer. This intermediate layer serves as a mediator that facilitates hole injection from the active layer into the electron barrier layer, reducing the direct impact of the large band gap on hole injection efficiency
3Reliability
If Mg is used as p-type dopant in the electron barrier layer to reduce hole injection impedance, then hole injection is improved, but light absorption increases and luminance efficiency is reduced
Solution Approach 1:
The patent changes the doping concentration parameter and thickness parameter of the electron barrier layer. By making the layer thin (2-7 nm) and optimizing the Mg doping concentration, the patent reduces the total amount of Mg present, thereby reducing light absorption while still maintaining sufficient hole injection capability through the thin barrier
Solution Approach 2:
The patent extracts or removes the Mg doping from the critical light-emitting region by confining it to a thin barrier layer (2-7 nm) that is spatially separated from the active layer where light is generated. This reduces the overlap between Mg-related light absorption and the emitted light wavelength
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 configuration achieves high luminance efficiency by minimizing electron overflow and crystal defects, improving differential efficiency and reliability, while maintaining effective hole injection and reducing light absorption.
Implementation Method 1
the electron barrier layer has a larger band gap than that of the active layer, and has a function of suppressing the overflow of the electrons
Implementation Method 2
it has been found out that when an intermediate layer having a small lattice constant is formed between the active layer and the electron barrier layer, the crystalline in the electron barrier layer is improved
Data Source
AI summary
A semiconductor light emitting device has a gallium nitride compound semiconductor, and a first cladding layer of a first conductivity type, an active layer, an electron barrier layer of a second conductivity type and made of InxAlyGa1-x-yN (0≦x≦1 and 0≦y≦1), and a second cladding layer of the second conductivity type, laminated, in order, on a substrate. The electron barrier layer has a larger band gap than each of the active layer and the second cladding layer. The thickness of the electron barrier layer is in a range from 2 nm to 7 nm.