In a semiconductor, the number density of intrinsic charge carriers at 27^° C is 1.5 × 10^16 / m^3. If the semiconductor is doped with impurity atom,…

In a semiconductor, the number density of intrinsic charge carriers at $\displaystyle 27^{\circ} \mathrm{C}$ is $\displaystyle 1.5 \times 10^{16} / \mathrm{m}^3$. If the semiconductor is doped with impurity atom, the hole density increases to $\displaystyle 4.5 \times 10^{22} / \mathrm{m}^3$. The electron density in the doped semiconductor is \_\_\_\_ $\displaystyle \times 10^9 / \mathrm{m}^3$.