Degradation of pHEMT performance in BiHEMTs caused by thermal history during
HBT growth and suggestions for improvement
Keywords: …pHEMT, MOVPE, BiHEMT, electron mobility, diffusion, uniform doping
The use of BiHEMTs, the integration of HBT & pHEMT, have resulted in high efficiency PAs. The mobility of the pHEMT in the BiHEMT structure was lower compared to simple pHEMTs in the development stage. It was found at careful investigation that Si from the delta-doped electron supply layer diffused into the InGaAs channel layer during HBT epitaxial growth. High mobility was obtained in the pHEMT by changing from delta doping to uniform doping.