In situ cleaning of GaAs and AlxGa1−xAs surfaces and production of ohmic contacts using an atomic hydrogen source based on a reflected arc discharge

Abstract

A method for the production of ohmic contacts to n-type GaAs and to n-type and p-type AlxGa1−xAs has been proposed where the surface cleaning in atomic hydrogen and the metal film deposition are performed in situ. A feature of the method is that it is realized in a system for vacuum deposition of metal films with the residual pressure kept equal to ∼5×10−4 or ∼(4–10)×10−5Pa when GaAs or AlxGa1−xAs structures, respectively, are cleaned. The atomic hydrogen flow was formed by a source whose operation is based on a reflected arc discharge with a hollow cathode and a self-heating electrode. In the process of cleaning the hydrogen pressure was 10−2 Pa and the temperature of the specimens and the time of their treatment were varied in the ranges from 300 to 400 °C and from 1 to 90 min, respectively. AuGe/GaAs interfaces with the contaminant content below the sensitivity threshold of the method of Auger electron spectroscopy (AES) have been produced. With some technological expedients, an AuGe/Al0.6Ga0.4As interface with the oxygen content <1% and the contents of other impurities below the sensitivity threshold of the AES method have been produced. A comparative investigation of the formation of an ohmic contact by the proposed method and by a conventional technology using “wet” chemical cleaning has shown that the contacts produced with the use of atomic hydrogen cleaning show a better morphology of the surface and a more even edge of the contact pad, high adhesion of the metal film to the semiconductor, and a low contact resistance. The technological process for the production of ohmic contacts is characterized by a high reproducibility. The application of the proposed method together with hydrogenation of the near-surface region of semiconductor structures used in the production of light diodes have raised the output power of the diodes by 30%–40%.