AlGaN/GaN heterojunction bipolar transistor structures-design considerations

The potential of III-nitride materials for the fabrication of bipolar trans istors is investigated theoretically. Several different AlGaN/GaN n-p-n het erojunction bipolar transistor structures are examined through calculations of their band profiles and majority carrier distributions in equilibrium a nd in forward active mode. Spontaneous and piezoelectric polarization charg es are utilized to create large hole sheet carrier densities in the base la yer, thus minimizing the base spreading resistance. At the same time, a lar ge accelerating field in the base can help reduce the base transit time of the electrons and, hence, increase the current gains of these devices. The temperature dependence of the hole concentration in the base is also invest igated. (C) 2000 American Institute of Physics. [S0021-8979(00)03114-5].