Photocurrent characteristics in p‐i‐n diodes with built‐in coupled or uncoupled multi‐quantum wells

Abstract

AbstractWe studied photocurrent characteristics in AlGaAs p‐i‐n diodes, where coupled or uncoupled GaAs/AlGaAs multi‐quantum wells (MQWs) were embedded in their intrinsic layers, to investigate how the electronic–coupling in the MQWs affects the device performance of MQW‐based solar cells. Measurements were done at 77 K to suppress thermal processes. When carriers were generated only in QWs, the photocurrent (PC) in the coupled MQW sample decreased substantially as soon as the forward‐bias voltage V is raised above ∼0.5 V and became almost zero at V ∼1 V. By contrast, in the uncoupled MQW sample the PC did not exhibit such a step‐like decrease but only gradually decreased up to V ∼1.2 V. This step‐like loss in PC observed in the coupled MQW structure is presumably attributable to the accumulation of photogenerated carriers in its MQW region. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)