Effect of finite quantum-well width on the compressibility of a two-dimensional electron gas

Double quantum-well structures have been used to measure the inverse compressibility (${\mathrm{\kappa }}^{\mathrm{-}1}$) of a two-dimensional electron gas as a function of the confining quantum-well width. The lower layer is contacted independently and carrier density changes within this layer are used to measure ${\mathrm{\kappa }}^{\mathrm{-}1}$ of the upper layer. As the well width increases we observe a decrease in ${\mathrm{\kappa }}^{\mathrm{-}1}$ which may be attributed to the effect of the Hartree term. The inclusion of Hartree effects produces the correct trend of ${\mathrm{\kappa }}^{\mathrm{-}1}$ with well width, although discrepancies still exist between the model and experiment.