ABSTRACT
Enhancement in the high frequency performance of transistors is dependent both on improved materials properties and smaller transit distances. This chapter investigates the effects of doping the channel of an AlInAs-GalnAs modulation doped transistor n and p type and evaluate the effect on the DC and RF characteristics of devices with 0.25 µm gate length. Assuming that the doping in the AlInAs donor layer is constant, the amount of charge transferred into the GaInAs remains the same independent of the acceptor concentration as it a function only of the component material band structures. The electric field at the interface is therefore constant. It is suggested that enhanced electron confinement and reduced source-drain space charge injection are the reason. Two-dimensional transistor analysis is required to fully exploit this approach and enhance the high frequency performance of HEMTs.
