| 1. |
- Grepstad, J. K., et al.
(författare)
-
As capping of MBE-grown compound semiconductors; novel opportunities to interface science and device fabrication
- 1994
-
Ingår i: Physica Scripta. - 0031-8949. ; 1994:T54, s. 216-225
-
Tidskriftsartikel (refereegranskat)abstract
- In situ condensation of an amorphous cap of the high vapour pressure element (i.e. As, Sb) has been found to provide effective protection of molecular beam epitaxy grown compound semiconductor surfaces against ambient contamination. Most work reported so far relates to arsenic-capped AlGaAs. Detailed investigation with surface sensitive structural (RHEED, LEED) and chemical (XPS) probes confirms that the protective cap is conveniently removed by annealing in ultrahigh vaccum environments at a temperature in excess of similar 350 °C. Clean AlxGa1-xAs(001) surfaces with different atomic reconstructions and corresponding (Al)Ga: As composition ratios are now routinely prepared by this technique, and thus offers an ideal testing ground for compound semiconductor surface and interface research. Reconstruction-dependent reactivity at metal/GaAs(001) interfaces is demonstrated, using surface sensitive synchrotron radiation photoelectron spectroscopy. Exploiting the protection offered by the As (Sb) cap for device fabrication purposes (e.g. in selective area epitaxy), demands a suitable method of pattern definition in the amorphous arsenic layer. The cap is shown to be chemically stable versus exposure to standard photolithographic processing chemicals, including photoresist, developer, and acetone (the photoresist solvent). However, the temperature required for thermal decapping is grossly inappropriate for photoresist curing. A novel technique of reactive decapping in a beam of hydrogen radicals (H‒) is shown to be effective at room temperature. This innovation makes pattern definition in the As cap compatible with standard photolithography, and test structures with similar 5 μm linewidth is demonstrated. Scanning electron micrographs unveil the presence of arsenic cap residues along the photoresist mask edges. Moreover, trace amounts of surface gallium oxide and carbon impurities were found with core-level photoelectron spectroscopy. The technique thus needs further refinement, before being useful in fabrication of compound semiconductor device structures.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Weman, Helge, 1960-, et al.
(författare)
-
Semiconductor Quantum-Wires and Nano-Wires for optoelectronic Applications
- 2009
-
Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 20:1, s. S94-S101
-
Tidskriftsartikel (refereegranskat)abstract
- Exciton transfer between two parallel GaAs V-groove quantum wires (QWRs) or two planar quantum wells (QWs) separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence (PL) and PL excitation (PLE) spectroscopy. It is found that the transfer is strongly reduced between the widely spaced QWRs as compared with QWs. We have also investigated the optical absorption in single QWRs embedded in an AlGaAs V-shaped channel waveguide. Using a combination of PLE and absorption measurements we construct the full dependence of absorption spectra on the linear polarization. Our studies reveal the importance of inter-subband mixing in determining the energies of the light-hole-like transitions and thus the QWR absorption. Finally we present recent results on the fabrication and structural characterization of GaAs and GaP nanowires (NWs) grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates, using Au-catalyzed vapor–liquid–solid growth technique. It is shown that, apart from optimizing the NW growth parameters, substrate material and the procedure for preparing the substrate before the MBE growth play an important role in controlling the NWs.
|
|
