Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster 1

HL 13.28: Poster

Monday, March 26, 2007, 15:00–17:30, Poster A

Doping efficiency and donor binding energy in high mobility AlAs quantum wells — Claudius Knaak, •Shivaji Dasgupta, Max Bichler, Anna Fontcuberta i Morral, Gerhard Abstreiter, and Matthew Grayson — Walter Schottky Institute, Technische Universität München, Am Coulombwall 3, Garching

We present a quantitative study of the energy band diagram for the X-point conduction band E_X for high mobility (001) oriented AlAs quantum wells (QW). Saturation of the dark electron density of the two dimensional electron system (2DES) was observed at 2× 10¹¹/cm² for an incrementally doped series of the samples, allowing the doping efficiency of the Si delta doping layers in Al_xGa₁−xAs (x =0.45) to be calibrated. In addition, we report the binding energy of the donors to be an essential factor in analyzing the conduction band diagram to explain the saturation density. In a double-sided doped AlAs QWs charging effects from dilute charge traps in the substrate [1] can be neglected because they will be screened by the bottom Si-delta doping layer. Our model is further complemented by a detailed study of the persistent photoconductivity. After a cold 4 K illumination, a peculiar rise in density to 4× 10¹¹/cm² is seen upon thermally annealing the samples in the dark at 40 K. Similar studies are also reported for high mobility (110) oriented AlAs QW substrates.

[1] De Poortere, et al. Phys. Rev. B 67, 153303 (2003).