Hybrid Si nanowire/amorphous silicon FETs for large-area image sensor arrays

Abstract

Silicon nanowire (SiNW) field-effect transistors were fabricated from SiNW mats mechanically transferred from a donor growth wafer. Top- and bottom-gate FET structures were fabricated using doped a-Si:H thin-film as the s/d contact. The off-current for the hybrid nanowire/thin-film devices was found to decrease by three orders of magnitude by using a graded doping profile for the a-Si:H source/drain contacts. Devices with the graded contacts had on/off ratios of > 105, field-effect mobility of 50 cm2/Vs, and sub threshold slope of 250 mV/decade. A two-inch diagonal 169180 pixel image sensor array was fabricated by integrating the SiNW backplane with an a-Si:H p-i-n photodiode.