of temperature: the fr roll-off with increasing current at higher temperatures becomes

Figure 2. Normalised fr(Jc) dependencies for various technologies, with a normalisation to 300 GHz (Bolognesi et al., 2001). Note the range of VeE biases and the clear manifestation of alloy potential blocking in the AllnAs/GalnAs DHBT despite the high collector voltage. In contrast, GalnAs and GaAs SHBTs feature a slow fr rolloff due to the Kirk effect.