GaN LED Tunnel Junction via Magnesium Desorption
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Solution Overview
Problem
The challenge in manufacturing GaN type light-emitting diodes lies in the difficulty of P-type doping due to deep acceptor levels, leading to low ionization of P-type dopants and low solubility of magnesium, which results in a significant concentration of magnesium in the NID GaN alloy layer, making it hard to form an operative tunnel junction.
Innovation Solution
A method involving vapour-phase epitaxial growth is used to deposit a P-doped AlGaN layer with a high concentration of magnesium, followed by a non-intentionally doped GaN layer, where the magnesium concentration is reduced by desorption in an atmosphere with reduced ammonia pressure, allowing for a sharp reduction in magnesium concentration and facilitating the formation of a conductive tunnel junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a P-doped GaN alloy layer is deposited using magnesium as dopant, then P-type doping is achieved, but magnesium concentration remains high in subsequent layers due to low solubility and slow reduction
Solution Approach 1:
The patent introduces an intermediate AlGaN layer between the P-doped GaN layer and the NID GaN layer. This intermediate layer segments the magnesium diffusion path, acting as a barrier that prevents excessive magnesium from reaching the NID layer while allowing the P-doped layer to maintain its required magnesium concentration for effective P-type doping.
Solution Approach 2:
The AlGaN intermediate layer serves as a mediator that controls magnesium transport. It has intermediate properties between the P-doped GaN layer (high magnesium) and the NID GaN layer (low magnesium), enabling gradual magnesium concentration reduction and preventing direct contamination of the NID layer.
2Reliability
If an nGaN alloy layer is deposited on pGaN alloy layer to form tunnel junction, then contact resistance is improved, but magnesium from pGaN layer contaminates nGaN layer making tunnel junction inoperative
Solution Approach 1:
The AlGaN intermediate layer acts as a protective intermediary between the P-doped GaN layer and the N-doped GaN layer intended for tunnel junction formation. It blocks magnesium diffusion to the N-doped layer, preserving the low-magnesium requirement for functional tunnel junction while still allowing the P-doped layer to achieve adequate doping.
Solution Approach 2:
The patent extracts the harmful magnesium contamination effect by introducing the AlGaN intermediate layer that selectively blocks magnesium diffusion. This extraction separates the magnesium source (P-doped layer) from the sensitive region (N-doped layer for tunnel junction), eliminating the contamination problem.
3Stability of the object's composition
If magnesium concentration is reduced slowly in NID layer, then diffusion equilibrium is maintained, but significant magnesium concentration persists over 100 nm thickness
Solution Approach 1:
The patent segments the magnesium diffusion path by introducing the AlGaN intermediate layer. This segmentation creates a stepped concentration profile with sharper transitions, confining the magnesium-affected region to a thinner effective zone while maintaining diffusion equilibrium through the graded composition of the intermediate layer.
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 method effectively reduces the magnesium concentration in the AlGaN layer, enabling the formation of a functional tunnel junction and improving contact resistance without altering the properties of the P-doped layer, thus enhancing the manufacturing efficiency of GaN light-emitting diodes.
Implementation Method 1
A method involving vapour-phase epitaxial growth is used to deposit a P-doped AlGaN layer with a high concentration of magnesium, followed by a non-intentionally doped GaN layer
Implementation Method 2
the magnesium concentration is reduced by desorption in an atmosphere with reduced ammonia pressure
Data Source
AI summary
A method for manufacturing a light-emitting diode is provided, including the following steps in succession, while maintaining a substrate in a vapour-phase epitaxial growth chamber: epitaxial deposition, with an atmosphere having a first non-zero concentration of ammonia in the chamber, of a first GaN alloy layer P-doped with magnesium; epitaxial deposition, on the first GaN alloy layer, of a sacrificial GaN alloy layer in a second atmosphere in the chamber that is not supplied with magnesium; placing the second atmosphere inside the chamber under conditions with a second concentration of ammonia that is at least equal to a third of the first non-zero concentration so as to remove the sacrificial GaN layer; and then epitaxial deposition of a second N-type doped GaN alloy layer so as to form a tunnel junction with the first GaN alloy layer.