Photoresponse spectra in p–i–n diodes containing quantum dots

The photoresponsivity spectra of a p–i–n diode comprising of a layer of quantum dots (QD) in the intrinsic region are measured for a wide range of wavelengths of light and applied voltages. The complex behaviour of the measured spectra is analysed taking into account different channels for electron and hole capture onto the QD and their escape dynamics. The photocurrent data are accompanied by measurements of dark conductivity which reveal both Sand Z-shaped current bistability. The phenomena are explained in terms of a QD charging effect. A model presented in this work shows that switching between the two current states of the first and second bistable regions is controlled by the charges stored in the QD.