Characterizing leakage current in silicon nanowire-based field-effect transistors by applying pseudo-random sequences

Development of miniaturized devices that enable rapid and direct recognition of small molecules has become a growing research area in various fields of nanotechnology. Silicon nanowire-based field-effect transistors (SiNW FETs) have been experimentally demonstrated for direct, label free, highly selective, and real-time detection of biological and chemical targets at very low concentrations. The detection of a target is based on the variation of conductance of the nanowire channel which is seen in the voltage-current behavior between the drain and source. Some current, known as leakage current, flows between the gate and drain, and affects the current between the drain and source in noise-like manner. The current is extremely low at DC, and can be ignored in most cases. Recent studies suggest, however, that the leakage current is likely to exhibit frequency-dependent characteristics. Recognizing such properties can possibly take great advantage in developing new detection technologies utilizing SiNW FETs. This paper applies the maximum-length binary sequence (MLBS) and spectrum method, and presents fast frequency-domain methods which can be used to measure and characterize the leakage current. Experimental measurements are shown from an n-type SiNW FET. The results clearly indicate the existence of the mentioned frequency-dependent characteristics.