Mesa p-n junction with field-effect dopant ionization
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Solution Overview
Problem
The efficiency of p-n junction optoelectronic devices, such as LEDs and photodiodes, is limited by high acceptor and donor activation energies in semiconductor materials like GaN and AlGaN, leading to reduced radiative efficiency and increased absorption of UV light, particularly in UV LEDs and UV photodetectors.
Innovation Solution
The introduction of a mesa structure with a p-n junction and an element capable of ionizing dopants through an electric field generation, enhancing the conductivity of p- or n-doped semiconductors, thereby increasing the internal quantum efficiency by ionizing acceptors or donors, even in materials with high activation energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If p-doped GaN is used to reduce acceptor activation energy, then the activation energy is reduced, but radiative efficiency in the active zone is limited and UV light absorption increases
Solution Approach 1:
The device is divided into functionally distinct regions: a p-doped GaN layer specifically designed to reduce acceptor activation energy, and a separate AlGaN active zone optimized for radiative efficiency. This segmentation allows each region to perform its specialized function without compromising the other, resolving the contradiction between reducing activation energy and maintaining radiative efficiency
Solution Approach 2:
Different doping concentrations and material compositions are applied to different regions of the device. The p-doped GaN layer has high doping concentration (10^19 to 10^21 cm^-3) to reduce activation energy, while the AlGaN active zone has optimized composition for radiative recombination. This local differentiation of properties resolves the contradiction by allowing each region to have the quality needed for its specific function
2Illumination intensity
If AlGaN with high aluminum concentration is used to form p-n junction, then UV light emission is achieved, but acceptor activation energy increases to 600 meV, reducing the quantity of activated acceptors
Solution Approach 1:
The device uses a composite structure combining GaN and AlGaN layers with different properties. The AlGaN layer provides UV light emission capability with appropriate bandgap, while the GaN layer provides lower acceptor activation energy. This composite material approach allows the device to achieve UV emission while avoiding the high activation energy penalty of high-Al AlGaN
Solution Approach 2:
The p-doped GaN layer acts as an intermediary between the AlGaN active zone and the contacts, providing a low activation energy path for carrier injection while allowing the AlGaN to maintain its UV emission properties. The GaN layer mediates the contradiction by providing a transition region with optimized electrical properties
3Quantity of substance
If high doping concentration is used to increase carrier availability, then more carriers are available for recombination, but current density increases and heating is generated
Solution Approach 1:
The device optimizes the doping concentration parameter to 10^19 to 10^21 cm^-3, which is sufficient to provide adequate carrier availability for recombination but below the threshold that would cause excessive current density and heating. This parameter optimization resolves the contradiction by finding the sweet spot between carrier availability and thermal management
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 significantly enhances the internal quantum efficiency of optoelectronic devices by increasing the number of available carriers for recombination, thereby improving emission or detection efficiency, especially in materials with high acceptor or donor activation energies, while minimizing current densities and reducing heating.
Implementation Method 1
an element capable of ionizing dopants of the p-n junction, or more precisely capable of ionizing dopants of the first and/or second portion of semiconductor, via a generation of an electric field in the p-n junction, or more precisely in the first and/or second portion of semiconductor
Implementation Method 2
capable of ionizing dopants of the p-n junction, or more precisely capable of ionizing dopants of the first and/or second portion of semiconductor
Data Source
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AI summary
optoelectronic device (100) comprising a mesa structure (124) including: - a first (106) and a second (108) semiconductor portions forming a pn junction, - a first electrode (112) electrically connected to the first portion which is disposed between the second portion and the first electrode, the device further comprising: - a second electrode (116) electrically connected to the second portion, - an element (118, 120) capable of ionizing dopants of the first and/or second portion via generation of an electric field in the first and/or second portion and covering at least a part of the lateral flanks of at least a part of the first and/or second semiconductor portion and at least a part of a space charge zone formed by the first and second portions, the upper faces of the first electrode and the second electrode form a substantially planar continuous surface (122).