Fig. 1. Schematic of the terahertz generation from metal-insulator-semiconductor heterostructure pumped by the ultrashort laser pulses

Fig. 2. Trends of carrier density generated by the laser pulses with different pulse durations

Fig. 3. Changing of the velocity of the carriers

Fig. 4. Terahertz pulses produced by laser pulse with different pulse durations. (a) Time-domain waveforms; (b) Corresponding spectra distribution

Fig. 5. Influence of the laser pulse duration on the (a) terahertz pulses central frequency and (b) bandwidth

Fig. 6. Influence of the carrier lifetime on (a) the terahertz pulse central frequency and (b)bandwidth

Fig. 7. The influence of semiconductor thickness in heterojunction on (a) the terahertz pulse central frequency and (b) bandwidth