The droplets are formed at low temperatures and high exciton densities, the latter of which can be created with intense optical excitation or electronic excitation in a p-n junction.
Evidence for electron-hole droplets was first observed by J. R. Haynes of Bell Labs in 1966,[1] who observed a frequency shift in the spectrum radiated by silicon at low temperatures (~3 K).
The shift was attributed to the recombination of a bound state of two excitons (electron-hole pairs).
A. Rogachev discovered metallic conduction in germanium at low temperatures when the density of excitons exceeded the amount required to transition into a metallic state.
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