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 (kappa(-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 kappa(-1) of the upper layer. As the well width increases we observe a decrease in kappa(-1) which may be attributed to the effect of the Hartree term. The inclusion of Hartree effects produces the correct trend of kappa(-1) with well width, although discrepancies still exist between the model and experiment.