Characterization of GaAs grown on SiGe/Si graded substrates using p-n junction diodes

The effect of GaAs buffer thickness on the electrical characteristics of a p+ - n- junction diode is presented. The GaAs diodes are grown on a Ge/graded Six Ge1-x /Si virtual substrate. Electrical characterization and visual observation provided vital insights into the origin of improvement in the electrical characteristics of the diode as the GaAs buffer thickness is increased. A high breakdown voltage of -9.2 V was achieved as the buffer thickness was increased from 50 to 600 nm, as the ideality factor reduces from 2.2 to 1.7, indicating reduction in the recombination current in the depletion region. This improvement is found to be related to the suppression mechanism of the wedge-shaped dislocation formation in the growth direction. This evidence provides important insights for the integration of III-V semiconductor devices, such as heterojunction bipolar transistor, with Si-based substrates.