Tunable far infrared absorption in logarithmically graded quantum wells

Abstract Compositional grading in the growth direction z of a GaAs/Al x Ga 1− x As heterostructure is used to simulate a potential well of the form V ( z ) = − a −2 ln ( abz + 1) + zb / a , where a and b are constants. Using both a front gate and an epitaxially grown back gate, we observe a large Stark shift from 35 to 125 cm −1 in the far infrared collective electronic resonant response by moving the electron gas through the asymmetric well.