Physics and Applications of SILICON/SILICON(1 - Germanium(x) Modulation Doped Structures
Abstract
We have investigated transport of electrons and holes at low temperature in Si/Si_{1-x}Ge_{x} modulation doped heterostructures. We used the properties of the two-dimensional hole gas to probe the Si/Si_{rm 1-x} Ge_{x} interface and fabricated symmetric p-type double heterostructures for the first time by rapid thermal chemical vapor deposition. We have also fabricated two-dimensional electron gases on graded relaxed Si_{1-x} Ge_{x} buffer layers with maximum low temperature mobility of 45,000 cm^2/Vcdot s, limited by the background doping in our reactor. We achieved the highest carrier density 2.8 times 10^{12} cm ^{-2} at 10 K and the lowest sheet resistivities 69 Omega/square at 10 K and 140 Omega/ square at 77 K. Using a two-mask self-aligned process, we fabricated modulation doped field effect transistors with low gate leakage currents at room temperature and maximum transconductance of 20 mS/mm limited by parasitic contact resistance. We have compared electron and hole transport and demonstrated alloy scattering in Si_{ 1-x}Ge_{x} strained channels to be the dominant scattering mechanism. From the experimental analysis, we established the empirical alloy scattering potentials of 0.8 eV for electrons and 0.6 eV for holes for the first time in two -dimensional strained Si_{1 -x}Ge_{x} layers. We propose strong intervalley coupling through alloy scattering and develop quantitative models for photoluminescence no-phonon line intensities and valley splitting energies in high magnetic fields.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- April 1994
- Bibcode:
- 1994PhDT........17V
- Keywords:
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- SILICON-GERMANIUM;
- ALLOY SCATTERING;
- Engineering: Electronics and Electrical; Physics: Condensed Matter