  Semiconductors are by now well-established targets for direct detection of
MeV to GeV dark matter via scattering off electrons. We show that semiconductor
targets can also detect significantly lighter dark matter via an absorption
process. When the dark matter mass is above the band gap of the semiconductor
(around an eV), absorption proceeds by excitation of an electron into the
conduction band. Below the band gap, multi-phonon excitations enable absorption
of dark matter in the 0.01 eV to eV mass range. Energetic dark matter particles
emitted from the sun can also be probed for masses below an eV. We derive the
reach for absorption of a relic kinetically mixed dark photon or pseudoscalar
in germanium and silicon, and show that existing direct detection results
already probe new parameter space. With only a moderate exposure, low-threshold
semiconductor target experiments can exceed current astrophysical and
terrestrial constraints on sub-keV bosonic dark matter.

High Energy Physics - Phenomenology;Cosmology and Nongalactic Astrophysics