Dependence of Modulation Amplitude on Electron Density in Unidirectional Lateral Superlattices: The Effect of the Thickness of the Two-dimensional Electron Gas

摘要

The amplitude V_0 of unidirectional periodic potential modulation introducedby a surface grating into a two-dimensional electron gas (2DEG) formed atAlGaAs/GaAs heterointerface is measured as a function of electron density n_eby analyzing commensurability oscillation of the magnetoresistance. Theelectron density is varied either by applying a bias to a metallic back gate orby illumination. The amplitude decreases with increasing density, with the rate|dV_0/dn_e| roughly an order of magnitude larger for the former method. Theresult is interpreted in terms of the rate, dE_1/d(delta E_c), of the change inthe first subband level E_1 in response to the variation of the conduction-bandedge delta E_c above the heterointerface. The rate crucially depends on thethickness of the 2DEG.