Consideration of the frequency performance potential of GaAs homojunction and heterojunction n-p-n transistors

Since the studies conducted by Milnes and Feucht (1972), it has been believed that heterojunction transistors have a higher frequency response than comparable homojunction structures. In the present investigation, a heterojunction transistor of nAlGaAs/pGaAs/nGaAs is compared with an n-p-n GaAs structure of similar dimensions. The individual effects of the base doping are considered in a properly weighted fashion. It is concluded that the heterojunction transistor is likely to exceed by less than 10 percent the frequency performance of the homojunction device. The modeling of the transistors is discussed, taking into account the maximum frequency of oscillation, and the reduction of lateral base resistance in the homojunction structure. It is found that the experimental evaluation of GaAs homojunction transistor performance is worth further attention.