\(\text{ Given: - The intrinsic carrier concentration } n_i = 1.5 \times 10^{16} \, \text{m}^{-3}, \\\)
\(\text{- Doping concentration of pentavalent atoms } N_d = \frac{5 \times 10^{28}}{10^5} = 5 \times 10^{23} \, \text{m}^{-3}.\\\)
\(\text{The number of holes } p \text{ in the doped semiconductor is given by:}\)
\(p = \frac{n_i^2}{N_d} = \frac{(1.5 \times 10^{16})^2}{5 \times 10^{23}} = 4.5 \times 10^8 \, \text{m}^{-3}\)
\(\text{Thus, the number density of holes is } 4.5 \times 10^8 \, \text{m}^{-3}.\)