Update 14_doping_and_devices_solutions.md

src/14_doping_and_devices_solutions.md

@@ -17,7 +17,7 @@ $$ n_e - n_h + n_D - n_A = N_D - N_A $$
 ### Subquestion 2
 
 Since $E_G \gg k_B T$, we can only use the law of mass action. 
-But the question offers us another piece of information - we are around $|N_D-N_A| ~ n_i$.
+But the question offers us another piece of information - we are around $|N_D-N_A| \approx n_i$.
 That means that we are near the transition between extrinsic and intrinsic regimes.
 However, we also know that dopants energies are quite small such that $E_C-E_A \ll E_G$ and $E_A-E_V \ll E_G$. 
 That means that we expect $n_i \ll n_D$ and $n_i \ll n_A$ (since both $n_i$ and dopant ionazition depends exponentially of the corresponding energy differences).