Patterned Quantum Dot Photosensitive FETs for Medium Frequency Optoelectronics

The use of colloidal quantum dots (CQDs) as active layers for the transistors in integrated circuits is often impeded by the poor compatibility of CQDs films with the standard lithographic processing. Successful patterning of tetrabutylammonium iodide-treated PbS CQDs films is demonstrated on (3-aminopropyl)triethoxysilane (APTES) functionalized glass or aluminum oxide surfaces, using lithography. Short-channel (4 mu m) field-effect transistors (FETs) with patterned gate electrode and patterned CQDs film as active layer with electron mobility of 0.1 cm(2) V-1 s(-1), threshold voltage of -0.29 V, and cutoff frequency of 400 kHz are demonstrated. Furthermore, the lithographic processing does not compromise the optical properties of the film, as evidenced by the photoresponse measurements of the FETs (11.6 mA W-1 at 920 nm and 26.7 mA W-1 at 440 nm). These results further demonstrate CQDs as a potential material for optoelectronic applications, where medium frequency operation is required.