Carrier concentration and mobility in B doped Si1−xGex (original) (raw)
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Applied Physics Letters, 1999
Hall-and-Strip measurements on modulation-doped SiGe heterostructures and combined Hall and capacitance-voltage measurements on metal-oxide-semiconductor ͑MOS͒-gated enhancement mode structures have been used to deduce Hall scattering factors, r H , in the Si 1Ϫx Ge x two-dimensional hole gas. At 300 K, r H was found to be equal to 0.4 for xϭ0.2 and xϭ0.3. Knowing r H , it is possible to calculate the 300 K drift mobilities in the modulation-doped structures which are found to be 400 cm 2 V Ϫ1 s Ϫ1 at a carrier density of 3.3ϫ10 11 cm Ϫ2 for xϭ0.2 and 300 cm 2 V Ϫ1 s Ϫ1 at 6.3ϫ10 11 cm Ϫ2 for xϭ0.3, factors of between 1.5 and 2.0 greater than a Si pMOS control.
Journal of Crystal Growth, 1997
B-doped Sio.95Geo.os(0 0 1) films were grown on Si(0 0 1) by gas-source molecular beam epitaxy in the surfacereaction-limited regime using Si2H6, Ge2H6, and B2H6. Incorporated B concentrations CB (5 × 1016 --3 × 1019 cm -3) were found to increase linearly with increasing B2H6 flux JB~H, (6 X 1012--2 × 1015 cm -2 s-1) at constant film growth temperature Ts, and to decrease exponentially with 1/Ts at constant JB2H6. The B2H 6 reactive sticking probability ranged from ~-3.3 × 10 -4 at Ts = 600°C to 8.2 × 10 -4 at 700°C and film growth rates were independent of JB~R,. Structural analysis by in-situ reflection high-energy electron diffraction combined with post-deposition high-resolution plan-view and cross-sectional transmission electron microscopy, high-resolution X-ray diffraction, and reciprocal lattice mapping showed that all films were fully strained, with measured relaxations less than the detection limit, -~ 3 × 10-5, and exhibited no evidence of dislocations or other extended defects. Room-temperature Sio.95Geo.os:B conductivity mobilities were equal to theoretical values and a factor of = 2 higher than corresponding results for bulk Si./~c varied from 410 cm 2 V-1 s-1 with CB = 5 x 1016 cm-3 to 60 cm 2 V-1 s-1 with Ca = 3 × 1019 cm-3.
Journal of Applied Physics, 1992
Silicon germanium (Si1−xGex) alloys have been grown by the floating zone method with x varying from 0.5 to 20 wt %. Resistivity and Hall effect measurements have been carried out in the temperature range 80–410 K. The Hall mobility has been found to decrease with Ge concentration varying between 0.5 and 4.5 wt % and thereafter an increase has been observed. The Hall mobility has also been found to decrease with an increase in temperature in these alloys following the AT−y relation, where A is a constant and T is the temperature in K.
Investigation of Properties of Highly Boron-Doped SiGe(C) Thin Layers
2000
A complex study of charge carrier transport, low-frequency noise and surface electric potential distribution of highly boron-doped SiGe(C) layers have been carried out. An attention is paid to the conceptual problem that from Hall-effect measurement for highly degenerated materials we can evaluate the Hall mobility, but for evaluation of mobile charge carrier density one needs to know the effective density of states at the Fermi level energy. The resistivity, Hall coefficient and hole Hall mobility have been measured at temperature range from 77 K to 350 K, while the surface electric potential distribution and the low-frequency noise spectra in the frequency interval from 10 Hz to 20 kHz at room temperature. It is shown that complex investigation of Hall mobility, low-frequency noise and surface electric potential distribution in highly doped SiGe(C) layers gives to one a powerfull diagnostic tool for quality characterization of these layers.
Investigation of the electron mobility in strained Si1-xGex at high Ge composition
Monte Carlo simulation of the low field electron mobility of strained Si and SiGe active layers on SiGe substrate is considered. The Ge mole fractions of both the active layer and the substrate are varied in a wide range. The linear deformation potential theory is used to calculate the shifts of the conduction band minima due to the uniaxial strain along [001]. The energy shifts and the effective masses are assumed to be functions of the Ge mole fraction. Finally, the ionized impurity scattering rate is generalized to include strain effects for doped materials.
Differential Hall characterisation of ultrashallow doping in advanced Si-based materials
Materials Science and Engineering: B, 2008
Strained Si channels are commonly used by manufacturers to enhance CMOS performance and research into novel channel materials (SiGe and Ge) is well underway. How these materials affect the electrical properties of the impurities used to dope them is largely unclear and the ability to accurately characterise dopant activation is key to finding this out. In the case of Si, since much is known about the relationship between carrier concentration and mobility, dopant activation can be assessed by competing techniques, however for the newer materials this information is not available. This paper demonstrates the differential Hall technique as a method capable of satisfying these gaps in our knowledge of dopant activation and mobility. Previously we have shown the technique, which combines Hall effect measurements with successive native oxide removal, can measure independent carrier and mobility profiles with resolution better than 1 nm for B-implanted Si and SOI. Presently we show the technique is extendable to characterise n-type dopants (Sb and As) and importantly, can be applied to novel substrates (focussing here on strained Si). In addition, the inherent assumption of the technique-uniform layer removal-is investigated and shown reasonable. Complementary ion beam analysis is used to show how we investigate and correct for Hall scattering effects and designated software is used to apply necessary corrections, transforming raw data into reproducible and highly resolved, carrier and mobility profiles.
Charge transfer in p+-Si / Si1-xGex modulation doped heterostructures grown by RTCVD
Microelectronic Engineering, 1994
High-quality Si/Sil_,Ge, simple (both normal and inverted) and double modulation doped heterostructures with 0~~~0.3 have been grown on Si(100) substrates by rapid thermal chemical vapor deposition (RTCVD) at low temperature (61O"C), using silane, germane and diborane in a hydrogen carrier gas. Hall measurements have been performed from 300 to 20 K and show the hole confinement in the Sir_,Ge, layer. The dependence of the confined density and hole mobility on germanium concentration and Si spacer thickness is presented. A simple calculation taking into account a single quantized energy level at each Si/SiGe interface has been made and yields confined densities in good agreement with experimental results. Magnetotransport measurements have been performed on several samples, and well defined Shubnikov de Haas oscillations and integral quantum Hall plateaus up to v=32 can be observed at 1.6 K in the magnetic field range 2-13 teslas. These data confirm the existence of a two dimensional hole gas at each Si/SiGe interface, with a density ranging from 3.1011 to 1012 cm-z, and a top mobility above 4000 cm2Ns, comparable to the best results obtained in similar MBE grown structures. Finally, these results demonstrate that high-quality p-type modulationdoped Si/Sil_,Ge, heterostructures can be grown by RTCVD at low temperature, and illustrate the latter's capabilities in terms of doping abruptness and interface quality.
Ge composition dependence of the minority carrier lifetime in monocrystalline alloys of Si1−xGex
Materials Science in Semiconductor Processing, 2006
In this work we have investigated the influence of the Ge composition on the minority carrier lifetime in Czochralski (Cz) grown monocrystalline Si 1Àx Ge x alloys in the composition range of 0oxo0.07. The lifetime measurements were performed by both microwave photo conductance decay (m-PCD) measurements and the quasi-steady-state photoconductance (QssPC) technique. Low-temperature (450 1C) anneals as well as phosphorous diffusion gettering were applied in order to investigate the possibility of improving the minority carrier lifetime in this material. A surface passivation method based on deposition of a double layer stack consisting of a hydrogenated amorphous silicon thin film capped by a silicon nitride anti-reflection coating was used. It is established that the minority carrier lifetime in the investigated alloys decreases dramatically with increasing Ge concentration. It is further shown that phosphorous gettering is the most effective method for the enhancement of bulk lifetime values in the Si 1Àx Ge x alloys studied. r