GaN Heterostructure Doping With Field-Assisted Mg Diffusion
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Solution Overview
Problem
Current methods for p-type doping of Gallium Nitride (GaN) face challenges such as high temperature requirements, equipment specificity, limited diffusion depths, and lattice damage, making it difficult to achieve efficient and selective area doping, especially for 3D structures.
Innovation Solution
A heterostructure design involving a substrate with a Group-III-nitride material, a dopant source layer, and a conductive cap layer, where an electric field gradient is established to facilitate low-temperature diffusion of magnesium (Mg) into GaN, allowing for p-type doping with minimal lattice damage and enabling doping of complex topologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ion implantation and high-temperature annealing are used for p-type doping of GaN, then dopant activation can be achieved, but the GaN lattice is severely degraded and decomposition occurs
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature annealing (>1200°C) to low-temperature annealing (700-900°C), and introduces a two-step process with separate doping and activation steps, enabling dopant activation without severe lattice degradation
Solution Approach 2:
The patent performs dopant implantation and formation of magnesium oxide layer before the annealing step, preparing the structure in advance so that low-temperature annealing can effectively activate the dopant without requiring high temperatures that cause lattice damage
2Reliability
If high-temperature annealing (>1200°C) is used to activate dopants in GaN, then dopant activation is achieved, but specialized equipment operating at high pressure and temperature is required
Solution Approach 1:
The patent reduces the annealing temperature from >1200°C to 700-900°C, which eliminates the need for specialized rapid thermal annealing equipment operating at high pressure and temperature, allowing use of conventional semiconductor processing equipment
Solution Approach 2:
The patent uses a magnesium oxide layer as a temporary sacrificial layer that facilitates low-temperature dopant activation and can be removed afterward, enabling the process to be performed with standard equipment rather than specialized expensive equipment
3Reliability
If repeated etching and growing steps are used to create sidewalls of 3D structures with p-type doped GaN, then p-type doping can be achieved, but the sidewall becomes susceptible to oxidation and degradation
Solution Approach 1:
The patent forms the dopant source layer and protective magnesium oxide layer on the sidewall before etching, so that during subsequent processing steps the dopant is already in place and protected, eliminating the need for repeated doping cycles that would expose the sidewall to oxidation
Solution Approach 2:
The magnesium oxide layer acts as an intermediary protective barrier on the sidewall, preventing direct exposure to oxidizing environments during etching and processing, thereby maintaining sidewall stability while enabling p-type doping
4Quantity of substance
If ion implantation is used for p-type doping of GaN, then dopant introduction is achieved, but the diffusion depth is limited and lattice damage occurs
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical/thermal diffusion process where magnesium diffuses from the magnesium oxide layer into the GaN substrate during low-temperature annealing, achieving deeper and more controlled doping profiles without the lattice damage associated with high-energy ion bombardment
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 enables efficient, low-temperature p-type doping of GaN with high carrier concentrations, suitable for various electronic and optoelectronic devices, including 3D structures, without the need for specialized equipment and minimizes lattice damage.
Implementation Method 1
an electric field gradient is established to facilitate low-temperature diffusion of magnesium (Mg) into GaN
Implementation Method 2
an electric field gradient is established within the source layer and the cap layer for causing diffusion
Implementation Method 3
Field assisted interfacial diffusion doping through heterostructure design
Data Source
AI summary
An apparatus includes a heterostructure including a substrate of Group-III-nitride material, a source layer including a dopant positioned on a surface of the substrate, and a conductive cap layer positioned on the source layer. A method of electric field-enhanced impurity diffusion includes obtaining a heterostructure including a substrate of Group-III-nitride semiconductor material, a source layer including a dopant positioned directly on the substrate, and a conductive cap layer positioned above the source layer, and applying a thermal annealing treatment to the heterostructure. An electric field gradient is established within the source layer and the cap layer for causing diffusion of an element from the substrate to the cap layer, and for causing diffusion of the dopant from the source layer to a former location of the element in the substrate thereby changing a conductivity and/or magnetic characteristic of the substrate.