Photonuclear Transmutation Doping in Gallium-Based Semiconductors
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Solution Overview
Problem
Current doping processes for gallium-based semiconductor materials, such as GaN, face challenges in achieving high-quality and uniform doping, particularly for p-type dopants, with existing methods like diffusion, ion implantation, and neutron transmutation having limitations in doping profile uniformity and requiring extensive modifications.
Innovation Solution
The use of photonuclear reactions, where gallium-based semiconductor workpieces are irradiated with gamma rays to transmute Ga into Zn or Ge, allowing for high-quality and uniform n-type and p-type doping, with the ability to penetrate deep and minimize structural damage, and the option to conduct doping after growth without radioactive byproducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If diffusion doping or ion implantation is used, then doping can be achieved, but the doping concentration gradient is too high with much higher concentration on the surface
Solution Approach 1:
The patent replaces mechanical/chemical doping processes (diffusion, ion implantation) with a nuclear transmutation process using photon irradiation. This substitution fundamentally changes the doping mechanism from surface-dominated transport to volumetric nuclear reaction, achieving uniform doping throughout the bulk material without surface concentration gradients.
Solution Approach 2:
The patent changes the fundamental parameter of the doping process from chemical/physical transport to nuclear transformation. By using photon-induced nuclear reactions to transmute Ga atoms into Zn or Ge dopants in-situ, the process achieves uniform doping concentration throughout the bulk material rather than the surface-gradient profile characteristic of conventional methods.
2Manufacturing precision
If doping during growth is used, then doping uniformity is improved, but extensive modifications to the growth process are required and wafer quality is affected
Solution Approach 1:
The patent performs doping as a separate post-growth step using photon irradiation, rather than attempting to incorporate doping during the growth process. This preliminary action (completing growth first, then doping) avoids the need for extensive modifications to the growth process while achieving uniform doping through nuclear transmutation of the already-grown GaN material.
Solution Approach 2:
The patent replaces the chemical/physical doping mechanisms inherent to growth processes with a nuclear transmutation process. This substitution eliminates the need to modify growth parameters and processes, as the doping occurs through photon-induced nuclear reactions in the finished material rather than through incorporation during growth.
3Manufacturing precision
If neutron transmutation doping is used, then uniform doping profile is achieved, but p-type doping cannot be achieved as Ga cannot be transmuted to Zn or other p-type dopants
Solution Approach 1:
The patent changes the irradiation parameter from neutrons to photons (gamma rays), which fundamentally alters the nuclear reaction pathways available. Photon irradiation enables both (γ,n) reactions for n-type doping and (γ,p) reactions for p-type doping, providing versatility in dopant type selection while maintaining uniform doping profiles through the bulk material.
Solution Approach 2:
The patent makes the doping process universal by using photon irradiation that can produce both n-type (Ge) and p-type (Zn) dopants from the same GaN substrate through different nuclear reaction channels. This multi-functional approach eliminates the limitation of neutron transmutation which could only produce n-type dopants, allowing flexible selection of dopant type based on device requirements.
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 provides highly uniform doping profiles for both n-type and p-type gallium-based semiconductor materials, enabling the production of high-quality wafers suitable for advanced semiconductor devices like vertical GaN power devices, with the added benefit of not requiring special handling due to non-radioactive materials post-irradiation.
Implementation Method 1
irradiating a gallium-based semiconductor workpiece with gamma rays to effect transmuting at least a portion of Ga in the workpiece to Zn and/or Ge
Data Source
AI summary
The present invention relates to various high quality n-type and p-type doped gallium-based semiconductor materials, electronic components incorporating these materials, and processes of producing these materials. In particular, The present invention relates processes to achieve high quality, uniform doping of a whole wafer or a thin layer of gallium-based semiconductor materials for various applications such as a vertical power transistor or diode.