Enhancement of mobility in pseudomorphic FETs with up and down monolayers

A comparison was made between three pseudomorphic FET channels. The control sample was a strained In/sub 0.15/Ga/sub 0.85/As quantum well bounded by undoped Al/sub 0.3/Ga/sub 0.7/As and GaAs with a 50-AA Al/sub 0.3/Ga/sub 0.7/As spacer and 5*10/sup 12/ Si planar doping. The second structure was identical to the first except one GaAs monolayer was replaced with one down monolayer. The third quantum well had one InAs down monolayer and two AlAs up monolayers positioned to increase the intersubband energy between the ground state and the next two states. The mobility was measured as a function of temperature from about 40 to 340 K for these structures. Some results are discussed.