Influences of surface sulfur treatments on the temperature-dependent characteristics of HBTs

The temperature-dependent DC characteristics of InGaP-GaAs heterojunction bipolar transistors with and without sulfur treatment are systematically studied and demonstrated. Due to the use of sulfur passivation, the series resistance of base-emitter junction of studied device can be effectively reduced. In addition, the device with sulfur treatment can be operated under ultra low collector current regimes (I_C≤10^-11 A). Experimentally, a long-time sulfur treatment is not appropriate. In this work, the studied device with sulfur treatment for 15 min is a good choice. Furthermore, at measured temperature (298 K-398 K), the studied device with sulfur treatment can reduce collector-emitter offset voltage and the impact of emitter size effect. Moreover, as the temperature is increased, the device with sulfur treatment will exhibit higher DC current gain and more stable temperature-dependent performances. This will extend the application regimes of the studied device in low-power and communication systems.