Abstract
We have combined numerous characterization techniques to investigate the growth of tensile-strained and n-doped Ge films on Si(001) substrates by means of solid-source molecular-beam epitaxy. The Ge growth was carried out using a two-step growth method: a low-temperature growth to produce strain relaxed and smooth buffer layers, followed by a high-temperature growth to get high crystalline quality Ge layers. It is shown that the Ge/Si Stranski-Krastanov growth mode can be completely suppressed when the growth is performed at substrate temperatures ranging between 260 °C and 300 °C. X-ray diffraction measurements indicate that the Ge films grown at temperatures of 700-770 °C are tensile-strained with typical values lying in the range of 0.22-0.24%. Cyclic annealing allows further increase in the tensile strain up to 0.30%, which represents the highest value ever reported in the Ge/Si system. n-Doping of Ge was carried out using a GaP decomposition source. It is shown that heavy n-doping levels are obtained at low substrate temperatures (210-250 °C). For a GaP source temperature of 725 °C and a substrate temperature of 210 °C, a phosphorus concentration of about 1019 cm - 3 can be obtained. Photoluminescence measurements reveal an intensity enhancement of about 16 times of the direct band gap emission and display a redshift of 25 meV that can be attributed to band gap narrowing due to a high n-doping level. Finally, we discuss about growth strategies allowing optimizing the Ge growth/doping process for optoelectronic applications.
Original language | English |
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Pages (from-to) | 70-75 |
Number of pages | 6 |
Journal | Thin Solid Films |
Volume | 557 |
DOIs | |
Publication status | Published - 2014 Apr 30 |
Keywords
- MBE growth
- Optoelectronics
- Tensile strain Ge
- n-Doping
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry