Electronic properties and defect levels induced by n/p-type defect-complexes in Ge

Defect-complexes are point defects that significantly influence the geometric, optical, and electrical properties of materials. Defect-complexes are known to improve the electronic and electrical properties of Ge. Deep and shallow defect levels in Ge have been linked to defect-complexes formed by the double self-interstitials and rare earth atoms. Despite 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, we present the results of the hybrid density functional theory calculations of substitutional and interstitial defect-complexes (BGeNi, NGeBi, AlGePi, PGeAli, GaGeAsi, AsGeGai, InGeSbi, and SbGeIni) in Ge. Their formation energies, electronic properties, defect-complex stability and induced defect levels in Ge 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 NGeBi and P(Ge)Al(i )essential donor levels were in the band gap of Ge. A shallow double acceptor defect level was found to be associated with the AlGePi , while the InGeSbi induced a shallow double donor defect level. The electrical inactive defect-complexes were the BGeNi , GaGeAsi , AsGeGai and SbGeIni. The results of this report are important, as they provide theoretical insight of the prediction of the n/p-type substitutional and interstitial defect-complexes in Ge.