NSM Archive  Silicon Germanium (SiGe)  Mobility and Hall Effect
Mobility and Hall Effect
Si_{1x}Ge_{x
}see also Si. Mobility and Hall Effect and Si. Mobility and Hall Effect 
Remarks  Referens  
Mobility electrons μ_{n}  (13964315x) cm^{2} V^{1} s^{1}  0 x 0.3, 300 K  Schaffler F. et al.(2001) 
Mobility holes μ_{p}  (450865x) cm^{2} V^{1} s^{1}  0 x 0.3, 300 K 
The mobility is influenceed by alloy scatttering witch contributes according to μ_{alloy} ~ T^{0.8}/(xx^{2}) (single crystals). Near band crossover (x0.15) intervalley scattering has to be taken into account.
Si_{1x}Ge_{x}. Electron Hall mobility vs.composition
at 300 K LandoldtBornstein (1982, 1987), Sasaki et al. (1984). 

Si_{x}Ge_{1x}. Intrinsic conductivity
vs.composition. T=300 K Busch & Vogt. (1960) 

Si_{x}Ge_{1x}. Electron Hall mobility
vs.composition. T=300 K open symbols  Busch & Vogt. (1960); Polycrystalline samples were employed in the range 0.3 < x < 0.8. 

Si_{x}Ge_{1x}. Electron Hall mobility
vs.composition. x < 0.3. Dashed curves  calculated mobilities for electrons in [100] and [111]valleys. Solid curve  both types of valleys into account and includes an arbitrary form of intervalley scattering Glicksman (1958) 

Si_{1x}Ge_{x}. Electron Hall mobility vs.composition.
T=300 K open symbols  Busch & Vogt. (1960); full symbols  LandoldtBornstein (1982, 1987) Polycrystalline samples were employed in the range 0.3 < x < 0.8. 

Si_{x}Ge_{1x}. Hole Hall mobility vs.composition.
T=300 K Busch & Vogt. (1960) 
TwoDimensional Electron Gas
The realization of a twodimensional electron gas in an Si/Si_{1x}Ge_{x} heterostructure requires a tensilely inplane strained quantum well for an efficient confinement of the electrons. To suppress alloy scattering, a strained Si quantum well on a cubic Si_{1x}Ge_{x} buffer layer with x around 30% is usually employed. Si_{1x}Ge_{x}. Evolution of the published
lowtemperature electron Hall mobilities. Twodimensional electron gas in modulationdoped strained Si quantum wells on relaxed Si_{1xs}Ge_{xs} barriers (xs 30%). Schaffler(1997) 

Si_{1x}Ge_{x}. Electron Hall mobility
vs. temperature of strained Si quantum wells on relaxed Si_{0.7}Ge_{0.3} For lower curve the mobility is limited by threading dislocations originating from the Si_{1x}Ge_{x} buffer layer. Upper curve  background doping limits the mobility. Sheet carrier densities for both curves are 7 x 10^{11} cm^{2}. Corrected room temperature mobility of the twodimensional carriers is 2500 cm^{2} V^{1} s^{1} Schaffler (1997). 

Si_{1x}Ge_{x}. Hall mobility vs. measured
carrier density. T= 300 K For comparison, the 300 K mobility of undoped bulk Si is marked Nelson et al. (1993). 

Si_{1x}Ge_{x}. Electron Hall mobility
vs. Si channel thickness for modulationdoped Si/Si_{0.7}Ge_{0.3}
heterostructures. T= 20 K The mobility drop beyond a channel of 100 A is caused by misfit dislocation formation in the channel. Ismail et al. (1994). 

Si_{1x}Ge_{x}. Calculated electron
mobilities vs. thickness of the undoped spacer layer between the doping
layer and the quantum well. T= 1.5 K, ΔE_{c} = 180 meV, N_{d}_{ }= 2 x 10^{18 }cm^{3} Dashed lines  acceptor background doping levels of 10^{14 }cm^{3} Solid lines  acceptor background doping levels of 10^{15 }cm^{3} Stern & Laux (1992). 

Si_{1x}Ge_{x}. Calculated carrier
concentrations vs. thickness of the undoped spacer layer between the
doping layer and the quantum well. T= 1.5 K, ΔE_{c} = 180 meV, N_{d}_{ }= 2 x 10^{18 }cm^{3} Dashed lines  acceptor background doping levels of 10^{14 }cm^{3} Solid lines  acceptor background doping levels of 10^{15 }cm^{3} Stern & Laux (1992). 
TwoDimensional Hole Gas
Twodimensional hole gases can be realized in pseudomorphic Si_{1x}Ge_{x}
layers on a Si substrate. The experimental mobilities, however, remain far behind
theoretical predictions.
An alternative route is the realization of pure Ge channels on a relaxed Si_{1x}Ge_{x}
buffer with 0.6 < x < 0.8, or of Gerich Si_{1x}Ge_{x}
channels (x < 0.7) on relaxed Si_{1x}Ge_{x}
buffers with 0.3 < x < 0.5. Room temperature mobilities of around
1000 cm^{2} V^{1} s^{1} where reported by Arafa
et al. (1996) for such a configuration with a Si_{0.3}Ge_{0.7}
channel.
Si_{1x}Ge_{x}. Lowtemperature hole
Hall mobilities vs. Ge content in pseudomorphic Si_{1x}Ge_{x}
quantum wells on Si substrates Data points  Whall (1995) Solid line  calculated curve for alloy scattering only, using a scattering potential of 0.74 eV Schaffler(1997) 

Si_{1x}Ge_{x}. Hole Hall mobility vs.
temperature in strained Ge channel on cubic Si_{0.3}Ge_{0.7}
buffer and in pseudomorphic Si_{0.87}Ge_{0.13} quantum well
Schaffler(1997) 