Nonalloyed and Alloyed Low-Resistance Ohmic Contacts with Good Morphology for GaAs Using a Graded InGaAs Cap Layer

摘要

Using a thin graded layer of InGaAs starting on GaAs and becoming InAs on the top, low-resistance alloyed and nonalloyed ohmic contacts have been achieved on N-GaAs epilayers grown by molecular-beam epitaxy on a semi-insulating GaAs substrate. In addition, by a suitable choice of the multilayer ohmic metals and by an optimization of the alloying process, good surface morphology was obtained. The transmission-line model is used to extrapolate contact resistances from measurements on test patterns with multiple gap spacings varying from 1 to 10 micrometers. Reprints. (jes)