BACKGATING EFFECTS IN GAAS-FETS WITH A CHANNEL-SEMI-INSULATING SUBSTRATE BOUNDARY

Several methods are presented to relate the backgating effects to hole traps near the channel-semi-insulating substrate interface of GaAs ME SFETs. By analysis of the variation of the individual properties of th e device the time dependence of backgating is shown to be related to t he time constants of these traps and the temperature dependence of bac kgating is related to the temperature dependence of the emission from these traps. The current between the semi-insulating substrate and the channel is shown to be dominated by a generation mechanism rather tha n the Trap Fill Limited model. This means that a space charge region e xists at the channel-substrate interface and the properties can be app roximated to an n-p(-) junction.