Abstract:
The importance given to bipolar transistors working at low temperature has grown up by means of BICMOS technology development. But, the great problem encountered during the realisation of BICMOS circuits working at low temperature is the low gain obtained The
heterojunction bipolar transistors provide a solution to this problem because they permit by use of silicium compatible technology (SiOe base) to accede to operating frequencies in the radiofrequency band (RF). It is about to model the electrical aspect of hetcrqjunctkm bipolar transistor using two means of simulation. The first one is digitally accomplished by SIBIDIF software, developed by the search team, which operates at ambient temperature. So, we have developed an additional module that permits to realise bidimensionnal simulation over a great temperature interval. In the second one, we have developed a programme that resolves in analytical manner the equations that govern the functioning of heterostructures at a variable temperature. A particular consideration is given to the study of the different components of the base current and the influence of the considered effects. Finally, we have compared the two models. The comparison of the obtained results is very satisfactory We have found that the temperature increasing favours the electrons injection from the emitter towards the base which induces the electrons injection within the collector and thereby the increasing of the collector current versus temperature. Moreover, the injection augmentation of the holes within the
emitter increases the base current.
