Resistivity changes caused by gold diffusion in epitaxial n-p-n transistors

Differential capacitance was used to determine resistivity changes in high-BVCEOn-p-n epitaxial transistor structures caused by gold diffusion and subsequent heat cycles. Resistivities corresponding to 8 × 10¹⁴to 2 × 10¹⁵phosphorus atoms/ cm³were found to be compensated to 10¹²/ cm⁸after a 15-min gold diffusion at 1150°C, with the degree of compensation diminishing after heat cycling at lower temperatures. Capacitance readings after gold diffusion were determined at forward bias to measure increments of depletion width. Gold concentrations were determined by radiochemical analysis and were correlated with diode lifetime measurements. A minimum lifetime value of 2 ns after gold diffusion could be increased to 14 ns by a low-temperature phosphorus emitter diffusion.