Comparison of intraband absorption and photocurrent in InAs/GaAs quantum dots

We present a comparative study of mid-infrared absorption and photocurrent measurements of self assembled InAs/GaAs quantum dots. A thermally activated bound/state-bound-state transition, as well as bound-wetting-layer and bound-continuum transitions are identified. By analyzing the temperature dependence of these transitions using absorption and photocurrent spectroscopies we are able to explain the previously reported discrepancies between the two measurement techniques. The activation energy (congruent to100 meV) for the bound-bound transition indicates that thermal escape of electrons occurs directly to continuum states. Evidence for preferential escape within the inhomogeneous distribution of dots is presented. (C) 2003 American Institute of Physics.