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General Properties

The following table summarizes many of the basic physical properties of Silicon, Germanium, and Silicon Germanium at different concentrations. The concentrations are given in the form of Si1-xGex where x represents the percent composition of Germanium.

Properties	Ge	Si.25Ge.75	Si.5Ge.5	Si.75Ge.25	Si
Atoms/cm3	4.42 x 1022 Ge	*4.415 x 1022	*4.61 x 1022	*4.805 x 1022	5.0 x 1022 Si
Atomic weight	72.60 Ge	*61.4725	*50.345	*39.2175	28.09 Si
Breakdown field (V/cm)	~105 Ge	*1.5 x 105	*2 x 105	*2.5 x 105	~3 x 105 Si
Crystal Structure	Diamond	Diamond	Diamond	Diamond	Diamond
Density (g/cm3)	5.3267 Ge	*4.577	*3.827	*3.078	2.328 Si
Dielectric constant	16.0 Ge	*14.975	*13.95	*12.925	11.9 Si
Effective density of States in conduction band, Nc (cm-3)		1.04 x 1019 Ge		2.8 x 1019 Si
Effective density of States in valence band, Nv (cm-3)		6.0 x 1018 Ge		1.04 x 1019 Si
Effective Mass, m*/ m0 Electrons Holes		ml= 1.64 mt= 0.082 ml h= 0.044 mh h= 0.28 Ge		ml= 0.98 mt= 0.19 ml h= 0.16 mh h= 0.49 Si
Electron affinity	4.0	*4.0125	*4.025	*4.0375	4.05

Properties

Si.25Ge.75

Si.5Ge.5

Si.75Ge.25

Minimum Indirect Energy Gap (eV) at 300K	0.66 Ge	***0.804	***0.945	***1.05	1.12 Si
Minimum Direct Energy Gap (eV)	.7 Ge	1.6	2.5	3.1	3.4 Si
Intrinsic carrier concentration (cm-3)	2.4 x 1013 Ge	*1.8 x 1013	*1.2 x 1013	*0.6 x 1013	1.45 x 1010 Si
Intrinsic Debye length (μm)	0.68 Ge	*6.51	*12.34	*18.17	24 Si
Intrinsic resistivity (Ω-cm)	47 Ge	*.575 x 105	*1.15 x 105	*1.725 x 105	2.3 x 105 Si
Lattice Constant (A)	***5.6575 Ge	***5.5960	***5.5373	***5.4825	***5.4310 Si
Linear coefficient of thermal expansion, ΔL/LΔT (°C-1)	5.8 x 10-6 Ge	*5.0 x 10-6	*4.2 x 10-6	*3.4 x 10-6	2.6 x 10-6 Si
Melting point (°C)	937 Ge	*1056.5	*1176	*1295.5	1415 Si
Minority carrier lifetime (s)	10-3 Ge	*1.375 x 10-3	*1.75 x 10-3	*2.125 x 10-3	2.5 x 10-3 Si
Mobility (drift) (cm2/V-s)	3900(electron) 1900(hole) Ge	3300(electron) 1537.5(hole)	7700(electron) 1175(hole)	2100(electron) 812.5(hole)	1500(electron) 450(hole) Si
Optical – phonon energy (eV)		0.037 Ge		0.063 Si
Phonon mean free path λ0(Å)		105 Ge		76 (electron) 55 (hole) Si
Specific heat (J/g-°C)	0.31 Ge	*.4075	*.505	*.6025	0.7 Si
Thermal conductivity at 300 K (W/cm-°C)	0.6 Ge	**.11	**.083	**.085	1.5 Si
Thermal diffusivity (cm2/s)	0.36 Ge	*0.495	*.63	*.765	0.9 Si
Vapor pressure (Pa)	1 at 1330°C 10-6 at 760°C Ge	1 at 1410°C 10-6 at 795	1 at 1490°C 10-6 at 830°C	1 at 1570°C 10-6 at 865°C	1 at 1650°C 10-6 at 900°C Si