The density of an electron-hole pair in a pure germanium is 3 × 1016 m-3 at room temperature. On doping with aluminium, the hole density increases to 4.5 × 1022 m-3. Now the electron density (in m-3) in doped germanium will be
1
1 × 1010
2
2 × 1010
3
0.5 × 1010
4
4 × 1010