Mobility and Hall Effect

Si1-xGex see also Si. Mobility and Hall Effect and Si. Mobility and Hall Effect		Remarks	Referens
Mobility electrons μn	(1396-4315x) cm2 V-1 s-1	0 x 0.3, 300 K	Schaffler F. et al.(2001)
Mobility holes μp	(450-865x) cm2 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/(x-x²) (single crystals). Near band crossover (x0.15) intervalley scattering has to be taken into account.

	Si1-xGex. Electron Hall mobility vs.composition at 300 K Landoldt-Bornstein (1982, 1987), Sasaki et al. (1984).
	SixGe1-x. Intrinsic conductivity vs.composition. T=300 K Busch & Vogt. (1960)
	SixGe1-x. 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.
	SixGe1-x. 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)
	Si1-xGex. Electron Hall mobility vs.composition. T=300 K open symbols -- Busch & Vogt. (1960); full symbols -- Landoldt-Bornstein (1982, 1987) Polycrystalline samples were employed in the range 0.3 < x < 0.8.
	SixGe1-x. Hole Hall mobility vs.composition. T=300 K Busch & Vogt. (1960)

Two-Dimensional Electron Gas

	Si1-xGex. Evolution of the published low-temperature electron Hall mobilities. Two-dimensional electron gas in modulation-doped strained Si quantum wells on relaxed Si1-xsGexs barriers (xs 30%). Schaffler(1997)
	Si1-xGex. Electron Hall mobility vs. temperature of strained Si quantum wells on relaxed Si0.7Ge0.3 For lower curve the mobility is limited by threading dislocations originating from the Si1-xGex buffer layer. Upper curve -- background doping limits the mobility. Sheet carrier densities for both curves are 7 x 1011 cm-2. Corrected room temperature mobility of the two-dimensional carriers is 2500 cm2 V-1 s-1 Schaffler (1997).
	Si1-xGex. 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).
	Si1-xGex. Electron Hall mobility vs. Si channel thickness for modulation-doped Si/Si0.7Ge0.3 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).
	Si1-xGex. Calculated electron mobilities vs. thickness of the undoped spacer layer between the doping layer and the quantum well. T= 1.5 K, ΔEc = 180 meV, Nd = 2 x 1018 cm-3 Dashed lines -- acceptor background doping levels of 1014 cm-3 Solid lines -- acceptor background doping levels of 1015 cm-3 Stern & Laux (1992).
	Si1-xGex. Calculated carrier concentrations vs. thickness of the undoped spacer layer between the doping layer and the quantum well. T= 1.5 K, ΔEc = 180 meV, Nd = 2 x 1018 cm-3 Dashed lines -- acceptor background doping levels of 1014 cm-3 Solid lines -- acceptor background doping levels of 1015 cm-3 Stern & Laux (1992).

Two-Dimensional Hole Gas

Two-dimensional hole gases can be realized in pseudomorphic Si_1-xGe_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_1-xGe_x buffer with 0.6 < x < 0.8, or of Ge-rich Si_1-xGe_x channels (x < 0.7) on relaxed Si_1-xGe_x buffers with 0.3 < x < 0.5. Room temperature mobilities of around 1000 cm² V^-1 s^-1 where reported by Arafa et al. (1996) for such a configuration with a Si_0.3Ge_0.7 channel.

	Si1-xGex. Low-temperature hole Hall mobilities vs. Ge content in pseudomorphic Si1-xGex 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)
	Si1-xGex. Hole Hall mobility vs. temperature in strained Ge channel on cubic Si0.3Ge0.7 buffer and in pseudomorphic Si0.87Ge0.13 quantum well Schaffler(1997)