RF properties of epitaxial lift-off HEMT devices

Epitaxial layers containing GaAs HEMT and P-HEMT structures have been lifted off the GaAs substrate and attached to other host substrates using an AlAs parting layer. The devices were on-wafer RF probed before and after the lift-off step, showing no degradation in the measured S-parameters. The maximum stable gain indicates a low frequency enhancement of the gain of 1-2 dB with some devices showing a consistent increase of F/sub T/ of 12-20% for all lifted-off HEMT structures. Comparison of the Hall measurements and small signal models show that the gain is improved and this is most probably associated with an enhanced carrier concentration.>