Rapid Thermal Techniques for Zinc Diffusion and Metal/Gallium Arsenide Alloying to Produce Low Resistance Ohmic Contacts

Abstract

ABSTRACTRapid thermal processing has been utilized to diffuse Zn into GaAs from a thin film zinc silicate source prepared by atmospheric pressure chemical vapor deposition (CVD). The zinc source was capped with ∼500 Å of silicon dioxide (SiO2 ). At 750°C for 20 sec, the diffusion of Zn reached a depth of 0.8 μm. For these diffusions, the diffusion constant is concentration dependent and is proportional to the square of the Zn concentration. Above 7500 C, anomalous secondary diffusion fronts were observed in the Zn diffusion profiles. A new model is proposed that explains the diffusion profiles at all temperatures. Ohmic contacts have been made to the above Zn-diffused surfaces using Cr/AuZn/Au metallizations. A typical value of the specific contact resistance is 8.0 × 10−7 ohm-cm2.