Contactless gating, surface charging and illumination effects in a buried Al0.24Ga0.76As/GaAs quantum well structure

The conductivity of an Al0.24Ga0.76As/GaAs quantum well was studied as a function of the surface charge generated by electron bombardment of the sample in the absence of an externally applied surface electric field. Under a suitable rate of electron irradiation, it was possible to completely shut off the conductive channel, implying a surface density n = 2.5 × 10 el/cm. Light illumination quenches the increase of the resistivity, apparently due to photoemission from the metastable surface states. Upon turning off the electron bombardment the surface charge on adsorbed layers of xenon and water at 8 K decays in room temperature darkness with a lifetime τ = 0.30 ± 0.02 s. The average charging efficiency, is μ0 0.001. Surface charging is shown to be an effective method for contactless gating of field effect devices. PACS. 73.20.-r Electron states at surfaces and interfaces – 73.40.-c Electronic transport in interface structures – 71.55.Eq III-V semiconductors