Conductivity Measurements in Hexagonal-Core Silicon Nanowire Transistors

The ability to control both the channel conductivity and the contact resistance of a silicon nanowire (SiNW) field-effect transistor by modulating the crystal phase during growth could open the door to new applications and performance tunability. Here, we present transport data in polytypic hexagonal-core cubic-shell single SiNW transistors and extract both their contact and channel resistance, comparing them to equivalent single-crystal (cubic) counterpart. A tunable volume of ordered stacking faults (hexagonality) during their VLS growth were introduced in the SiNW. We show that in these hexagonal-core nanowires there is a decrease in channel conductivity, mainly due to a reduction of charge carriers available in the silicon channel (from 10¹⁹ cm^-3 in single-crystal to 10¹⁷ cm^-3 at high hexagonal volume). We also demonstrate an increase in Schottky barrier height between the metal contacts and the hexagonal-core SiNW as a function of the hexagonal volume fraction (from 0.54 eV to 0.67 eV).