Search

We demonstrate transitions of hopping behaviors for delocalized electrons through the discrete dopant-induced quantum dots in n-doped silicon junctionless nanowire transistors by the temperature-dependent conductance characteristics. There are two obvious transition platforms within the critical temperature regimes for the experimental conductance data, which are extracted from the unified transfer characteristics for different temperatures at the gate voltage positions of the initial transconductance g m peak in V g1 and valley in V g2. The crossover temperatures of the electron hopping behaviors are analytically determined by the temperature-dependent conductance at the gate voltages V g1 and V g2. This finding provides essential evidence for the hopping electron behaviors under the influence of thermal activation and long-range Coulomb interaction.

Single and multiple n-channel junctionless nanowire transistors (JNTs) are fabricated and experimentally investigated at variable temperatures. Clear current oscillations caused by the quantum-confinement effect are observed in the curve of drain current versus gate voltage acquired at low temperatures (10 K–100 K) and variable drain bias voltages (10 mV–90 mV). Transfer characteristics exhibit current oscillation peaks below flat-band voltage (VFB) at temperatures up to 75 K, which is possibly due to Coulomb-blocking from quantum dots, which are randomly formed by ionized dopants in the just opened n-type one-dimensional (1D) channel of silicon nanowires. However, at higher voltages than VFB, regular current steps are observed in single-channel JNTs, which corresponds to the fully populated subbands in the 1D channel. The subband energy spacing extracted from transconductance peaks accords well with theoretical predication. However, in multiple-channel JNT, only tiny oscillation peaks of the drain current are observed due to the combination of the drain current from multiple channels with quantum-confinement effects.