Hot-carrier injection in step-drift rf power LDMOSFET

In this paper, hot-carrier effect in step-drift RF LDMOSFET is investigated. Due to the lower electric field close to the channel region, substrate current with the step -drift design is much lower than in a single-drift design. However, this is achieved at the expense of transconductance. Furthermore, a second origin of hot-carrier generation is found at the location of step drift. It is demonstrated that, instead of causing bias drift, hot-carrier injection at the step drift influences the voltage and current sweep range. In particular, negative charge can cause degradation of saturation current and breakdown voltage. As a result, power capability decreases during the lifetime of RF amplifier. Transconductance performance degradation at high current levels is also observed, which leads to reduced gain at high power levels.