EPR studies of intrinsic and impurity-related defects in the

II-IV-V2 compounds: ZnGeP2 and ZnSiP2

W. Gehlhoff

Institute for Solid State Physics, Technical University Berlin, Hardenbergstr. 36,

D-10623 Berlin, Germany

 

 

II-IV-V2 compounds are ternary semiconductors with a chalcopyrite structure and have been studied in the last years mainly for their potential as nonlinear optical material for frequency-conversion applications in the near and mid-infrared region. While ZnGeP2 is an established NLO material, the direct use of ZnSiP2 for such frequency-conversion ap­plications is quite restricted. However, the development of optically confined birefringent chalcopyrite heterostructures favors at present the system ZnGeP2–ZnSiP2 lattice-matched on GaP or Si substrate. The most II-IV-V2 are also viable candidates for future spintronic devices, because of their ferromagnetic behavior at room temperature when heavily doped with Mn or other transition metals (TM’s). Both infrared frequency con­version and spintronic application are affected by native defects. The ferromagnetism ob­served or predicted for highly doped II-IV-V2 compounds might result from the interac­tion of the magnetic TM ions on the different group II and IV sites with holes produced by native defects and charge compensation.

Magnetic resonance studies of the properties of native defects in ZnGeP2 and their energy level positions in the band gap are reviewed and first results above such defects in ZnSiP2 are presented. The contributions of the dominant native defects to the optical absorption band of ZnGeP2 crystals are revealed by photo-EPR investigations in combination with the first ODMR experiments. The EPR results above Mn in the II-IV-V2 chalcopyrites are summarized and new results concerning the incorporation of Fe at different sites and various charge states in ZnGeP2 are discussed. The observation of some new Mn centers, the first experimental detection of the anti-ferromagnetic coupled Mn-M pairs in ZnGeP2 and new results concerning the local change of the free parameter xf of the chalcopyrite structure by Mn doping are presented.