= Solution
\b[The ambient-temperature <Fermi level> is raised into the upper part of the gap, toward the conduction-band edge, relative to intrinsic silicon.] The sample is an <n-type semiconductor>: ionized donors supply many more <conduction electrons> than the intrinsic population.
For a nondegenerate, substantially ionized sample with negligible acceptors, $n\simeq N_D$. With <effective density of states> $N_c$, the conduction-band relation gives
$$
n=N_c e^{-(E_c-\mu)/(k_BT)},
\qquad
\boxed{\mu\simeq E_c-k_BT\ln\frac{N_c}{N_D}}.
$$
Because a few ppm normally gives $N_D\ll N_c$ at ambient temperature, the <chemical potential> remains below the conduction-band edge rather than entering it as in a strongly <degenerate semiconductor>. Its precise position requires the dopant density, <density of states> and degree of ionization; the broad qualitative shift is fixed by donor doping.
It is \b[not necessary for $\mu$ to lie between the donor level and the conduction edge]. In a substantially ionized nondegenerate sample, the <chemical potential> can lie below the shallow donor level, as in the illustrative diagram. Donor ionization is determined by the level's occupation relative to $\mu$; a finite-temperature Fermi level is not the highest filled one-electron level of every individual configuration.
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