  Layered transition metal dichalcogenide (TMD) materials, i.e. 1T-TiSe$_2$ and
2H-NbSe$_2$, harbor a second order charge density wave (CDW) transition where
phonons play a key role for the periodic modulations of conduction electron
densities and associated lattice distortions. We systematically study the
transport and capacitance characteristics over a wide temperature range of
Schottky barriers formed by intimately contacting freshly exfoliated flakes of
1T-TiSe$_2$ and 2H-NbSe$_2$ to \textit{n}-type GaAs semiconductor substrates.
The extracted temperature-dependent parameters (zero-bias barrier height,
ideality and built-in potential) reflect changes at the TMD/GaAs interface
induced by CDW formation for both TMD materials. The measured built-in
potential reveals chemical-potential shifts relating to CDW formation. With
decreasing temperature a peak in the chemical-potential shifts during CDW
evolution indicates a competition between electron energy re-distributions and
a combination of lattice strain energies and Coulomb interactions. These
modulations of chemical potential in CDW systems, such as 1T-TiSe$_2$ and
2H-NbSe$_2$ harboring second-order phase transitions, reflect a corresponding
conversion from short to long-range order.
