Electro-Absorption and Refraction by Electron Transfer in Asymmetric Modulation-doped Multiple Quantum Well Structures.

Abstract

Remarkable changes in the absorption spectrum of n-type modulation doped quantum wells (QW) are produced by varying the electron concentration inside the QW in field effect structures1,2. In the vicinity of the gap, the dominant process is phase space filling. It results in a bleaching of the exciton resonances and a net blue shift of the absorption edge, similar to the Bumstein-Moss shift seen in bulk materials. So far the effect was only demonstrated on single QW, where the carriers were moved in the plan, in and out of the deplition region of a Schottky contact3,4. In this paper we present and demonstrate a novel concept of electric field driven electron transfer in and out of a multiple period QW structure by providing a reservoir of charges in close proximity to each QW. We report measurements of the differential absorption and the refraction associated with this electron transfer in a 10 Reservoir-QW period.