Wide electron gas with periodic density modulation

Abstract

We report the growth and characterization of a high-quality wide (∼2000 Å) three-dimensional electron gas (3DEG) with periodic density modulation (period ∼200 Å) in a modulation-doped wide parabolic potential well with a superimposed superlattice. Computer-controlled molecular beam epitaxy is used to synthesize the potential well as a graded AlxGa1−xAs digital alloy. The density-modulated 3DEG is compared to a uniform 3DEG of the same average density and width in a parabolic well without the superlattice. The Al mole fraction profiles for the two samples are measured in calibration runs immediately prior to actual growths. The density-modulated 3DEG has a low-temperature in-plane mobility in excess of 105 cm2/V s, compared to ∼2×105 cm2/V s for the uniform 3DEG. Capacitance-voltage measurements directly reveal the modulation of the density of the electron gas in the parabolic well with superimposed superlattice, and the absence of any density modulation for the gas in the bare parabolic well.