Rapid Thermal Alloyed Ohmic Contacts to p‐Type GaAs

Abstract

A systematic study of Au/Zn/Au ohmic contacts to Be‐implanted p‐type by rapid thermal alloying is presented. The processing conditions, such as zinc composition and temperature‐time cycle, are optimized. For the peak hole concentration, about , contact resistivity as low as is obtained. The microstructure of the contact is investigated using SEM, EDXA, AES, and XRD measurements in order to explore the correlation of the structural information with electrical characteristics represented by contact resistivity. It is found that during alloying, the layer near the interface is decomposed due to Ga and As outdiffusion, enhanced by Au interdiffusion. Ga diffuses to the contact surface in a much larger extent than As does. The interaction of Au and Ga, which produces phase, plays a key role in the formation of alloyed ohmic contacts to . The rapid thermal processing technique provides better control of Au‐Ga reaction, as well as limited dissolution of the surface, which makes the optimum ohmic contact possible. The present work has demonstrated that rapid thermal alloying offers obvious advantages over the conventional furnace alloying process, including lower contact resistivity, better interface morphology by limiting interfacial liquid phase reaction, and controlled shallow penetration depth.