Dependence of modulation amplitude on electron density in unidirectional lateral superlattices: The effect of the thickness of the two-dimensional electron gas

The amplitude V-0 of unidirectional periodic potential modulation introduced by a surface grating into a two-dimensional electron gas (2DEG) formed at AlGaAs/GaAs heterointerface is measured as a function of electron density n(e) by analyzing commensurability oscillation of the magnetoresistance. The electron density is varied either by applying a bias to a metallic back gate or by illumination. The amplitude decreases with increasing density, with the rate vertical bar dV(0)/dn(e)vertical bar roughly an order of magnitude larger for the former method. The result is interpreted in terms of the rate, dE(1)/d(delta E-c), of the change in the first subband level El in response to the variation of the conduction-band edge E-delta(c) above the heterointerface. The rate crucially depends on the thickness of the 2DEG.