Epitaxial Al on δ-doped GaAs: a reproducible and very thermally stable low resistance non-alloyed ohmic contact to GaAs

A new approach to fabricating very reproducible and extremely stable non alloyed ohmic contacts to n-GaAs is reported.The technique relies on the use of surface δ-doping and epitaxial Al metallisation. The advantages of this new type of ohmic contact are :

Very low specific contact resistivity (< 10⁶ Ωcm⁻²).

Thermal stability up to 550 °C.

Abrupt interfaces with GaAs with virtually no chemical reactions or interdiffusion leading to penetration depths of less than 90 Å (compared with 2000 Å for the Au-Ge contact).

Al metallisation allowing submicron patterns to be achieved.

Simplicity of fabrication and reproducibility.

This approach open up the way to hybrid configurations in MESFETs were the epitaxial Al can be used as both the gate and source and drain metallisations.