Electron-hole liquid in germanium under high〈111〉stress

The properties of the electron-hole liquid (EHL) in Ge are examined as a function of uniaxial 〈111〉 stress with use of spectral and temporal measurements of the electron-hole–recombination luminescence. We are the first to observe the EHL phase in the high-stress limit (σ≳70 kgf/${\mathrm{mm}}^2$, where 1 kgf/${\mathrm{mm}}^2$==10 MPa) at T=2 K, based on fits to calculated spectral line shapes. The dependence of the measured EHL densities on uniaxial 〈111〉 stress agrees well with that predicted by sophisticated many-body calculations. Measurements of the EHL lifetime are also reported for uniaxial 〈111〉 stresses from 5.6 to 23.9 kgf/${\mathrm{mm}}^2$. The density dependence of the EHL lifetime indicates a constant value for the electron-hole enhancement factor, $g_{\mathrm{eh}}$(0), for electron-hole–pair densities>3.5×${10}^{16}$ ${\mathrm{cm}}^{\mathrm{-}3}$. This result disagrees with theoretical predictions, but is consistent with experimental results reported by others.