Thermal neutron transmutation doping of GaN semiconductors

High quality Ge doping of GaN is demonstrated using primarily thermal neutrons for the first time. In this study, GaN was doped with Ge to concentrations from 1016 Ge atoms/cm3 to 1018 Ge atoms/cm3. The doping concentrations were measured using gamma-ray spectroscopy and confirmed using SIMS analysis. The data from SIMS analysis also show consistent Ge doping concentration throughout the depth of the GaN wafers. After irradiation, the GaN was annealed in a nitrogen environment at 950 °C for 30 min. The neutron doping process turns out to produce spatially uniform doping throughout the whole volume of the GaN substrate.

Improvement of Semiconductors Quality Using Isotopic Nanoengineering

The article covers a solution of a modern electronics problem: improvement of data transmission device speed using the example of fiber-optic communication lines (FOCL). The data processing rate and throughput of transmission channels are determined by capabilities of the optoelectronics and, first of all, by the performance of its hardware components. The article presents all possible ways to improve the performance of FOCL. Design and production of communication devices moves to the nanotechnological level that opens up new possibilities for creation of semiconductors with advanced characteristics. The methods and means chosen for production of the nanostructures are crucial for creation of the new generation hardware components. Graphene is considered as the most promising material for creation of the new generation hardware components for semiconductors. Potential capabilities of the material are not yet fully explored. Isotopic nanoengineering is used as the method for production of the nanostructures with improved characteristics. In particular, we use the neutron transmutation doping technology based on irradiation of a graphite sample with a neutron flux. This method increases content of the 13C isotope (natural graphite contains only about 1.1% of this isotope). As a result, the band gap opens bringing the properties of the material closer to the properties of a semiconductor. The closer the width of the graphene band gap to the width of the silicon band gap, the closer the properties of graphene to the properties of semiconducting silicon. Furthermore, all properties of the natural graphite (high throughput and sensitivity to almost the entire optical spectrum) are preserved.

Promising Neutron Irradiation Applications at the High Temperature Engineering Test Reactor

The high temperature gas-cooled reactor (HTGR) has advantages for irradiation applications such as large space available for irradiation at reflector region and high thermal neutron spectrum with the graphite moderator. High temperature engineering test reactor (HTTR), a prismatic type of the HTGR, has been constructed to establish and upgrade the basic technologies for the HTGRs. Many irradiation regions are reserved in the HTTR to be served as a potential tool for an irradiation test reactor in order to promote innovative basic researches such as materials, fusion reactor technology, and radiation chemistry. This study shows the overview of some possible irradiation applications at the HTTRs including neutron transmutation doping silicon (NTD-Si) and Iodine-125 (125I) productions. The HTTR has possibility to produce about 40 tons of doped Si-particles per year for fabrication of spherical silicon solar cell. Besides, the HTTR could also produce about 1.8 × 105 GBq/yr of 125I isotope, comparing to 3.0 × 103 GBq of total 125I supplied in Japan in 2016.