becoz Si and Ge are indirect bandgap semiconductors. for lasing action direct bandgap semiconductors are required of the type In Ga As P
1.Bandgap is comparatively large hence suitable for low & high temp. 2.High melting point of si makes it stable over wide temp. 3.si is more freely available in nature. 4.leakage current less than ge.
For Si it is 0.6or 0.7 and for Ge 0.3 or 0.2.Both values correct for both si and ge
Si can be fabricated into ICs inexpensively, Ge cannot.Si maximum junction operating temperature is 150C, Ge is only 70C.Si is as cheap and plentiful as sand, Ge is more expensive and rarer.etc.
Ge
Mg. I is a non-metal and Si and Ge are metalloids.
Ge has higher conductivity than Si. Because at room temperature the electron and hole mobility for Ge is larger than those of Si. Another explanation is the lower band gap of Ge than Si.
the energy required to break covalent bond in si is 1.1ev and in ge is 0.7ev
for germanium it is 0.3 and for silicon it is 0.7
格雷格(ge lei si )or 格瑞格(ge rui si)
0.6-0.7 V for Si at room temp. and 0.3 for Ge at room temp.
silicon has a wider bandgap than germenium .silicon jeakage current small, easily available then Ga and break down voltage is more. knee voltage of si is 0.7and Ga is having 0.3then Si is very useful.