Photo-excited states in germanium at liquid-helium temperatures

Technical Report · Wed Dec 01 00:00:00 EST 1982

DOI:https://doi.org/10.2172/6555016· OSTI ID:6555016

Culbertson, J C

A wide variety of experimental work dealing with the basic properties of photoexcited states in Ge at liquid helium temperatures is presented. The primary emphasis is on the electron-hole liquid (EHL) and the free exciton (FE). The EHL is composed of two interpenetrating Fermi liquids, one of electrons and one of holes, each with its own Fermi level. The FE dealt with here is a mobile, loosely bound state of an electron and a hole. We report the first absolute measurement of the density dependence of the enhancement factor g/sub eh/(0) for the EHL in Ge. This factor g/sub eh/(0) is a measure of the electron-hole spatial correlation function, and provides a valuable and sensitive test for the predictions of various many-body-theory approximations. An EHL droplet - FE gas system confined to a strain induced potential well was used. The measurement approach relied on only a few simple and verifiable assumptions. A byproduct of this work was the measurement as a function of stress of: the electron and hole Fermi levels E/sub F//sup e/ and E/sub F//sup h/, the EHL density n/sub l/, the condensation energy phi of a FE relative to the EHL, and the binding energy of a FE (E/sub x/) relative to free carriers (FC). The decay of a FE-FC system confined to a strain induced potential well is studied. The first direct measurement of the FE diffusivity D/sub x/ is reported. The evolution in time of spatial profiles of FE luminescence were measured. From these FE density profiles, D/sub x/(4.2K) approx. = to 300 cm/sup 2/ s/sup -1/, the surface recombination velocity S approx. = 3000 cm s/sup -1/, and the FE lifetime tau/sub x/ = 27 ..mu..s with surface effects excluded were determined. (WHK)

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6555016
• Report Number(s): LBL-15472; ON: DE83006188
• Resource Relation: Other Information: Portions are illegible in microfiche products. Thesis
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
GERMANIUM
EXCITONS
FERMI GAS
PHOTON COLLISIONS
BAND THEORY
BINDING ENERGY
CRYSTALS
DIFFUSION
ELECTRON-HOLE DROPLETS
ENERGY GAP
EXCITED STATES
FERMI LEVEL
LUMINESCENCE
ULTRALOW TEMPERATURE
COLLISIONS
ELEMENTS
ENERGY
ENERGY LEVELS
METALS
PLASMA
QUASI PARTICLES
SOLID-STATE PLASMA
656001* - Condensed Matter Physics- Solid-State Plasma