Self-consistent calculations of [111]-oriented GaAs and InP based pseudomorphic HEMT´s

Band structure calculations, charge distribution and charge control properties in InGaAs-based pseudomorphic modulation doped [111]-FET´s are presented. Compressive strain in AlGaAs-InGaAs-GaAs structures, and both tensile and compressive strains in AlInAs-InGaAs-InP devices are used to generate internal electric fields via the piezoelectric effect. Normal and inverted HEMT´s with maximum. Charge in the well and minimized parallel conduction have been designed using this piezoelectric internal field. Improvements in charge concentration (up to 50% more) and its distribution in the well (almost centered) are achieved in this new orientation. Transconductance and gate capacitance versus gate voltage are compared for the [100] and [111] orientations. We conclude that the device performance is improved when the [111] substrate is used