Offstate Current
The flow of electric charge that persists through a semiconductor junction when an external voltage is applied in the non-conducting direction defines the baseline noise of the device. This flow is called reverse bias leakage current and represents a major source of power dissipation and error in silicon sensors. It consists of both diffusion and generation components.
The total magnitude depends on temperature, material defects, and junction area.
Voltage Dependency
Increasing the applied voltage widens the depletion region and causes the generation current to rise. This change makes the reverse bias leakage current dependent on the operating voltage until breakdown occurs. Voltage regulation is necessary to maintain a stable leakage baseline in sensitive transimpedance amplifiers.
Metrological Boundary
Precision measurements of this current require highly shielded test fixtures to prevent external electromagnetic interference. Low-noise source measure units must resolve currents in the picoampere range during sensor qualification. This testing confirms compliance with the maximum leakage specifications.
Mitigation Technique
Guard rings and surface passivation reduce the leakage by intercepting surface currents before they reach the signal terminal. Implementing these structures keeps the reverse bias leakage current within acceptable limits for high-performance photodetectors. Silicon-on-insulator platforms offer further reduction by eliminating substrate leakage paths.
