Deactivation of electrically supersaturated Te-doped InGaAs grown by MOCVD

Achieving and sustaining the highest doping level possible in InGaAs is critical for the reduction of contact resistance in future microelectronic applications. Tellurium (Te) is a very promising n-type dopant with high reported n-type doping densities. However, the stability of this dopant during post-growth thermal processing is unknown. Supersaturated Te-doped InGaAs layers were grown by MOCVD at 500 °C. The electrically active concentration of Te doping was 4.4 × 1019 cm−3 as grown. The thermal stability of the Te was investigated by studying the effect of post-growth annealing between 550 and 700 °C on the electrical activation. At all temperatures, the electrical activation decreased from its starting electron concentration of 4.4 × 1019 cm−3 down to 6–7 × 1018 cm−3. The rate of deactivation was measured at each temperature, and the activation energy for the deactivation process was determined to be 2.6 eV. The deactivation could be caused by either Te–Te clustering or a Te-point defect reaction. HAADF-STEM images showed no visible clustering or precipitation after deactivation. Based on previous ab initio calculations that suggest the VIII population increases as the Fermi level moves toward the conduction band, it is proposed that formation of isolated point defect complexes, possibly a Te–VIII complex, is associated with the deactivation process.