Solution-Grown Nanowire Devices for Sensitive and Fast Photodetection

Highly sensitive and fast photodetector devices with CdSe quantum nanowires as active elements. have been developed exploiting the advantages of electro- and wet-chemical routes. Bismuth nanoparticles electrochemically synthesized directly onto interdigitating platinum electrodes serve as catalysts in the following solution-liquid-solid synthesis of quantum nanowires directly on immersed substrates under mild Conditions. at low temperature. This fast and simple preparation process leads to a photodetector device with a film Of nanowires of limited thickness bridging the electrode gaps, in which a high fraction of individual nanowires are electrically contacted and can be exposed to light at the,same time The high sensitivity of the photodetector device can be expressed by its on/off ratio of its photosensitivity of more than 10(7) over a broad wavelength range up to about 700 nm. The specific detectivity and responsivity are determined to D* = 4 x 10(13) Jones and R = 0.32 A/W, respectively. The speed of the device reflects itself in a 3 dB frequency above 1 MHz corresponding to rise and fall times below 350 ns. The remarkable combination of a high sensitivity and a fast response is attributed to depletion regions inside the nanowires, tunnel-junction barriers between nanowires, and Schottky contacts at the electrodes, where all of these features are strongly influenced by the number of photogenerated charge carriers.