Trivalent Atom Defect-Complex Induced Defect Levels in Germanium for Enhanced Ge‑Based Device Performance

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发表日期：

2024年1月26日

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Emmanuel Igumbor,
Moise Dongho-Nguimdo,
Edwin Mapasha,
Rajendran Kalimuthu,
Abdulrafiu Raji,
Walter Meyer

摘要

Defect complexes have a significant impact on the structural, electronic, optical and electrical properties of semiconductors. Several defect complexes formed by n-type and p-type atoms in Ge have been implemented for the development of improved modern microelectronic devices. However, there is no reported study on the substitutional-interstitial defect complexes formed by trivalent atoms in Ge. This paper presents a hybrid density functional theory study of the structural, electronic, formation and defect levels induced by the trivalent substitutional-interstitial (B $_\textrm{Ge}$ $_{Ge}$ B $_\textrm{i}$ $_{i}$ , Al $_\textrm{Ge}$ $_{Ge}$ Al $_\textrm{i}$ $_{i}$ , Ga $_\textrm{Ge}$ $_{Ge}$ Ga $_\textrm{i}$ $_{i}$ and In $_\textrm{Ge}$ $_{Ge}$ In $_\textrm{i}$ $_{i}$ ) defect complexes in Ge. The formation energy results showed that the trivalent substitutional-interstitial defect complexes in Ge were formed with relatively low energy. Ga $_\textrm{Ge}$ $_{Ge}$ Ga $_\textrm{i}$ $_{i}$ under equilibrium conditions is the most energetically favourable, with a formation energy of 3.95 eV. All trivalent atoms are bound with their respective substitutional and interstitial atoms without dissociation. With respect to their ability to form as a defect cluster, the In $_\textrm{Ge}$ $_{Ge}$ In $_\textrm{i}$ $_{i}$ is the most stable defect complex, with a binding energy of 2.91 eV. Except for the Ga $_\textrm{Ge}$ $_{Ge}$ Ga $_\textrm{i}$ $_{i}$ , all studied defect complexes are electrically active. The B $_\textrm{Ge}$ $_{Ge}$ B $_\textrm{i}$ $_{i}$ and Al $_\textrm{Ge}$ $_{Ge}$ Al $_\textrm{i}$ $_{i}$ induced a single acceptor level, while the In $_\textrm{Ge}$ $_{Ge}$ In $_\textrm{i}$ $_{i}$ induced active donor levels. The acceptor defect level induced by the B $_\textrm{Ge}$ $_{Ge}$ B $_\textrm{i}$ $_{i}$ is deep, and that of the Al $_\textrm{Ge}$ $_{Ge}$ Al $_\textrm{i}$ $_{i}$ is shallow, close to the conduction band. The results of this study are important, as they provide theoretical insights into the experimental characterization of the substitutional-interstitial defect complexes formed by trivalent impurities in germanium, which could help to improve Ge-based microelectronic devices.