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Description
Defect-complexes are point defects that significantly influence the geometric,
optical, and electrical properties of materials. The presence of defect-complexes
in Ge have been reported to be electrically active and influence the performance of its device. Despite of this breakthrough, several defect-complexes in Ge are not well understood; hence may pose as a challenge to the optimal performance of Ge based devices. In this study, hybrid density functional theory calculations of substitution and interstitial defect-complexes in Ge were performed. Their formation energies, electronic properties, defect-complex stability and induced defect levels were predicted. While the formation energies of the defect-complexes formed by the P and Al atoms were relatively low and energetically more favourable, those defect-complexes formed by the B and N atoms were the least energetically favourable. Except for the BGeNi, all the defect-complexes significantly bound with energies lower than their formation energies. The BGeNi and NGeBi behaved as p-type semiconductors, whereas the SbGeIni, AsGeGai, and PGeAli exhibited n-type semiconductor characteristics. The NGeBi, AlGePi and PGeAli essential donor levels were in the band gap of Ge. A shallow double acceptor level was found to be associated with the AlGePi, while the InGeSbi induced a shallow double donor defect level. The results of this report are important, as they provide insight for the control of n/p-type substitution and interstitial defect-complexes in Ge during synthesis and characterization.
