Ohmic contacts to n-GaAs using graded band gap layers of Ga1−xInxAs grown by molecular beam epitaxy

Abstract

Ohmic contacts were studied on structures which utilize the fact that for InAs surfaces Fermi level pinning occurs at or in the conduction band. It was found that an epitaxial layer of n-Ga1−xInxAs grown by molecular beam epitaxy on n-GaAs which is graded in composition from x = 0 at the GaAs interface to 0.8?x?1.0 at the surface will produce a structure with a nearly zero Schottky barrier height for the metal–Ga1−xInxAs interface and hence a low resistance ohmic contact. A transmission line measurement of non-alloyed contact resistance of 5×10−7<Rc<5×10−6 ohm cm2 was obtained for a Ag/n-Ga1−xInxAs/n-GaAs MESFET structure.