High pressure as a tool to study electron localization

We have used high pressure to investigate resonant tunnelling in a single-b arrier, n-i-n GaAs/ A1As/GaAs diode with an embedded layer of InAs self-ass embled quantum dots (SAQD). We have obtained convincing evidence for resona nt tunnelling through individual Gamma -valley-related electron states that we associate with the SAQD. The tunnel current through a SAQD was used as a local probe of a localized phase of a two-dimensional electron system in the accumulation layer of the diode. We have found evidence that at low den sities, the localized electrons form relatively large, high-density cluster s.