Currents of the GaInPGaAs heterojunction bipolar transistor as a function of the temperature

The behavior of the collector and base currents, as a function of the temperature, of the GaInPGaAs heterojunction bipolar transistor shows that the emitter-base junction is a gradual one, and that the base diffusion current is due to injected holes into the emitter. At room temperature, the emitter and base band gaps at the places where the carrier injection takes place are just ∼13 meV different. Such a band gap difference introduces a temperature dependence of the device current gain, which decreases as the temperature increases, leading to almost no difference on it for the "as-grown" and "current stressed" devices at operating temperatures higher than 130 °C.