Detrimental effects limiting the performances of InP HEMT-based OEICs

An investigation has been carried out on InAlAs/InGaAs HEMTs dedicated to monolithic optoelectronic integrated circuits (OEICs) for receiver as well as transmitter applications. The monolithic integration on InP semi-insulating substrates can be penalized by several parasitic effects related to trapping/detrapping mechanisms originated in the substrate and/or buffer layers. These parasitics have been studied in three MBE-grown HEMT structures, one of them previously demonstrated as efficient in the reduction of the gate current induced by an impact ionisation mechanism developing in the InGaAs channel layer.