Photovoltaic and optoelectronic properties of InAs(1 0 0)-based photoconductive cells with quantum dots and nanopits

The low bias and room temperature mid-infrared photoconductive cells (PCC) made of n-InAs(1 0 0) crystals and epitaxial films with and without quaternary InAsSbP quantum dots (QDs) and nanopits on the PCC active surface are developed, fabricated and investigated. The liquid phase epitaxy (LPE) is applied either for the growth of epitaxial films, or for nucleation of the QDs-nanopits cooperative structures. High-resolution SEM and AFM techniques are used to investigate the size, shape and distribution density of the QDs and nanopits. Anomalous photovoltaic (PV) effect is detected in PCC with quaternary QDs (type II band alignments) and nanopits as well as the qualitative physical explanation are proposed. The PCC open-circuit voltage and short-circuit current are measured at room temperature versus output radiation power density of the He–Ne continuously operated laser at different (λ = 3.39, 1.15 and 0.63 μm) wavelengths, as well as versus the distance from the “black-body” heat source with the surface of 1 cm2 and different temperatures. The current–voltage characteristics and photoresponse spectra of the developed PCCs are measured and investigated. We showed that the formation of the QDs-nanopits cooperative structures on the n-InAs(1 0 0) surface leads to the increasing of the PCC’s electrical sheet resistance up to one order, as well as results in shift of the photoresponse spectrum towards the long wavelength region. The QDs-based PCC’s voltage and current responsivity at room temperature are equal 1.5 V/W and 1 mA/W, respectively, at zero bias and λ = 3.39 μm monochromatic radiation.