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Projekt Druckansicht

Helium-ähnliche Störstellenzentren in Silizium und Germanium: Wechselwirkung mit Infrarotstrahlung, Nichtgleichgewichtsverteilungen und optoelektronische Anwendungen

Fachliche Zuordnung Experimentelle Physik der kondensierten Materie
Förderung Förderung von 2018 bis 2021
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 389056032
 
Erstellungsjahr 2021

Zusammenfassung der Projektergebnisse

The project was focused on the experimental and theoretical investigation of the infrared characteristics of multiple-charge impurity centers in elemental semiconductors. Intracenter transitions of double donor centers in silicon, double and triple acceptors in germanium, falling in the 3-30 µm wavelength range, provide information on excited states, their relaxation rates, and have a potential for light emission in view of possible optioelectronic applications. These properties were planned to be accessed by high-resoluton infrared absorption spectroscopy, infrared electronic Raman scattering, magneto-optical spectroscopy, time-resolved spectraoscopy, and photoluminescence studies of the impurity centers. While such impurity centers are known for decades, many of their features were not explained, some of them were not found before, and some were not thought to exist. The main drawback in this research area was the moderate quality and little diversity of research-grade materials. Pushing diffusion doping technology to its up-to-date capability, using the world’s purest original crystals for doping, varying isotopic content, combining interstitial and substitutional dopants, combining high-sensitive analytical techniques for characterization and delivering systematic feedback to technology has provided a range of new and diverse research grade Si:Mg samples, that enabled most of reported scientific results. The main results achieved in the frame of this project are: 1. Comprehensive ingsights in the structure of impurity states and the energy spectrum as a whole for an interstitial Mg donor in Si, forming isolated atomic donor centers, donors by paring of Mg with other isolated elements and Mg cluster complexes. First evidence of para- and ortho-states of isolated neutral helium-like interstitial Mg donors in Si was obtained by infrared absorption and photoconductive spectroscopy. Fingerprint photoluminescence spectra of Mg revealed a Mg-pair isoelectronic bound exciton. Pairing of interstitial double Mg with substitutional single acceptors formed shallow donor centers with a hydrogen-like energy spectrum. Revisiting the Mg* center explained its spectrum of excited states and the uncommon fine structure of its ground state revealed a symmetry, never observed for donors in cubic semiconductors. A new class of shallow Mg-related donors, preliminary assigned to clustered complexes, has been observed. 2. Investigations of the dynamics of infrared ultrafast resonant excitation of multiple-charge double donors in Si showed significally longer (ns time scale) lifetimes of the excited states of deep chalcogen donors as compared to shallower single-electron centers. In contrast, more shallow Mg double donors in Si have faster relaxation rates, which we assign to enhanced multiple-phonon-assisted relaxation of excited states. 3. Photo-thermal conductivity spectra of Si doped by deep double chalcogens showed a complex structure combining overlapping diescrete intracenter transitions of molecular donors and state continuum of photoionization of neutral atomic donors with alternate contributions to the integral photocurrent depending on the Stark effect strengthen at impurity resonances. A significant extension, up to a factor of 2-3, of the spectral range of the photoconductive response has been obtained in Si crystals co-doped by several shallow, group V, centers together with deeper, group IIa, atoms. The obtained results provide important contributions in the knowledge of the energy spectrum of interstitial double donors in cubic semiconductors. Different co-doping techniques for Si and Ge as developed in this project enable a broad range of manipulation of intracenter spectra of multiple-charge centers, that can be used for dedicated optoelectronic applications.

Projektbezogene Publikationen (Auswahl)

 
 

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