Semiconductors with higher carrier mobility and carrier density are required to fabricate a p–n junction diode for high-speed device operation and high-frequency signal processing. Here, we use a chemically doped semiconducting single-walled carbon nanotube (SWCNT) random network for a field effect transistor (FET) and demonstrate a rectifier operated at a wide range of frequencies by fabricating a p–n junction diode. The p–n diode was fabricated by using a pristine p-type SWCNT-FET where half was covered by SiO₂ and the other half was chemically doped by using benzyl viologen molecules, which was converted into an n-type channel. The half-wave rectifier of the random network SWCNT p–n junction diode clearly highlights the device operation under high input signal frequencies up to 10 MHz with very low output distortion, which a commercial silicon p–n junction diode cannot access. These results indicate that the random network SWCNT p–n junction diodes can be used as building blocks of complex circuits in a range of applications in microelectronics, optoelectronics, sensors, and other systems.