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THE DEFECTS IN SEMICONDUCTORS

semiconductor defects

Gallium nitride (GaN) is the world’s second-most preferred semiconductor, present in devices ranging from light-emitting diodes and photodetectors to high-temperature electron mobility transistors. When these devices are exposed to irradiation from high-energy particles – as they often are in fields such as satellite communications, aerospace, defence and the nuclear industry – they are prone to develop defects that degrade their electronic properties.

Researchers at East China Normal University in Shanghai and Shanxi University in Taiyuan have now performed the first systematic study of a class of(GaN) defects known as defect pairs. Such structures have been studied to date, and the researchers say that understanding them and the mechanisms that cause them may help boost the radiation resistivity of (GaN-based) devices.

The 21 different types of defect pairs in semiconductors

The properties of these point defects have been well-studied over the last three decades. However, defects of this type can also bind with each other to form less-common defects, including double-site defect pairs and multiple-site defect complexes. In principle, 21 different types of defect pairs can form, each with its own structural configuration.

Fortunately for (GaN) device designers, these exotic defect pairs usually require much higher energy to form than single-point defects. Freshly-synthesized GaN typically contains them only in low concentrations, and for this reason only a handful of defect pairs, such as VGa-VN and VGa-GaN, have been studied in any detail.

In radiation-damaged samples, however, the concentration of the high-energy defect pairs can be much greater. This led Shiyou Chen and his colleagues to study all 21 defect pairs in (GaN), performing first-principles calculations of their structures, formation energies and transition energy levels.

Their results show that after a high-energy particle strikes the (GaN) and triggers a defect-inducing “collision cascade”, the defect pairs that form are generally stable. Such pairs are separated by short distances and nine of them have formation energies lower than 10 eV. In terms of their effect on the material’s properties, they mostly act as electron donors, producing many defect levels in the band gap of GaN and potentially impairing the performance of GaN-based devices.

Semiconductors and Electronics

Formation of defect-pairs in GaN under high-energy particle irradiation.

Gallium nitride (GaN) is the world’s second-favourite semiconductor, present in devices ranging from light-emitting diodes and photodetectors to high-temperature electron mobility transistors. When these devices are exposed to irradiation from high-energy particles – as they often are in fields such as satellite communications, aerospace, defence and the nuclear industry – they are prone to developing defects that degrade their electronic properties.

Researchers at East China Normal University in Shanghai and Shanxi University in Taiyuan have now performed the first systematic study of a class of GaN defects known as defect pairs. Such structures have been little studied to date, and the researchers say that understanding them and the mechanisms that cause them may help boost the radiation resistivity of GaN-based devices.

For equipment in low-Earth orbit, the most common forms of damaging radiation are proton, electron and gamma radiation. In a nuclear-industry context, the chief culprit is usually radiation from neutrons. These high-energy particles can create a dizzying array of defects in GaN, including point defects, defect pairs and complexes, and disordered regions in the material’s semiconductor lattice. The point-defect “family” alone contains six sub-types of defect, known as VGa and VN vacancies, GaN and NGa anti-sites and Gai and Ni interstitials.

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10 Comments

  1. Reply

    Cool

  2. Profile photo ofSIRMUSTY

    Reply

    nice info

  3. Reply

    awesome….

  4. Reply

    Nice info

  5. Reply

    Nice info, thanks for sharing

  6. Reply

    Nice post

  7. Profile photo ofExcel01

    Reply

    Semiconductors

  8. Reply

    Nice

  9. Reply

    Thanks for the education

  10. Reply

    Interesting

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