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Optische Eigenschaften von verdünnten magnetischen Halbleitern auf GaN-Basis
| Content Provider | Semantic Scholar |
|---|---|
| Author | Zenneck, Jan |
| Copyright Year | 2008 |
| Abstract | Various GaN-based diluted magnetic semiconductors (DMS) were characterized in the course of this work. The main topic was GaMnN and there especially the relation between growth conditions and optical properties. The main analysis tool was photoluminescence (PL), for which an experimental setup optimized for GaN was developed and put into use.The basis for the optical measurements was structural characterization, where a second phase could be detected in XRD. With the help of TEM-measurements it could be identified as GaMn3N. For the whole parameterspace of GaMnN-growth therefore a growth window was identified, where diluted GaMnN with up to 5% Mn content could be achieved without precipitation. XRD rocking curves and Raman measurements showed a reduced crystal quality of GaMnN compared to GaN, but even this problem could be overcome by the use of a sapphire substrate with a MOCVD-grown GaN buffer-layer.With these results in mind, the PL spectra of the GaMnN samples were analyzed. Existence and width of the excitonic lines showed a clear correlation between optical and structural measurements concerning the crystal quality. Due to the high optical quality Mn could be identified as a deep acceptor in GaN via PL-measurements. Magneto-optical measurements at the free excitonic lines in GaMnN show a weak coupling of the local Mn-spins with the GaN matrix. This is a key property for the construction of spin injectors with the help of DMS.Another new field for research was opened by the identification of the intra-3d transition 5E → 5T2 of Mn3+ at 1.41 − 1.42 eV in PL-spectra of GaMnN. This transition was thoroughly characterized and compared to the known absorption data in the literature. Due to the unsurpassed optical quality of the samples on sapphire substrate, the zero phonon line was deconvoluted into three different peaks. Absorption measurements on the same samples gave proof of the charge state Mn3+ in our samples. This state with partially filled d-orbitals is the basis for the so called double-exchange, one of the theoretical models for a GaN-based DMS. As the intra-3d transition in our samples broadens and then vanishes with increasing Mn-content, this can be seen as an indication for this type of magnetical coupling.In addition to GaMnN two other GaN-based DMS were analyzed. GaCrN samples exhibited an infra-red luminescence signal very similar to GaMnN. Localized at 1.19 eV it could be attributed to an intra-3d transition of Cr4+ and thus the 10 year-old struggle for the identification of this signal was resolved. GaGdN showed no Gd-specific signals, but a shift of the near-bandedge luminescence with increasing Gd-content. With the help of Raman measurements compressive strain was identified to be the cause of this shift. When the Gd-content reaches the regime of more than 1%, a bandgap narrowing is detectable. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://ediss.uni-goettingen.de/bitstream/handle/11858/00-1735-0000-0006-B46D-3/zenneck.pdf?sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
