The keys to get high transconductance of AlGaAs/InGaAs/GaAs pseudomorphic HEMTs devices

There are two key points to get high transconductance of pseudomorphic HEMT S (pHEMTs) devices. From the point view of materials, the transfer efficien cy of the electrons from the delta -doped AlGaAs layer to the InGaAs channe l must be high. From the point view of device processing, the gate recess d epth must be carefully controlled. In the present work, AlGaAs/InGaAs/GaAs pHEMTs structures were grown by molecular beam epitaxy. Layer structures of the pHEMTs were optimized to get high transfer efficiency of the electrons . Gate recess depth was also optimized. A 0.2 mum pHEMT was fabricated on t he materials with optimized layer structure using the optimized gate recess depth. The maximum transconductance of 650 mS/mm and the cut-off frequency of 81 GHz were achieved. (C) 2001 published by Elsevier Science Ltd.