CHARACTERISTICS OF MESA-ISOLATED AND LOCOS-ISOLATED MOLECULAR-BEAM EPITAXY SIGE DIODES

Molecular beam epitaxy grown p+-n SiGe-Si heterojunction diodes with a nd without p+ Si caps on top of the p+ SiGe have been fabricated on n- type Si[100] wafers with and without SiO2 LOCOS patterns. It is shown that the p+Si caps create p+-p+ Si-SiGe isotype heterojunctions in ser ies with the p+-n SiGe-Si heterojunctions. Potential barriers and carr ier depletion regions exist in the isotype heterojunction regions owin g to the band-gap difference between the two materials. Effects of the LOCOS and the p+-p+ Si-SiGe isotype heterojunction in series with the p+ -n SiGe-Si heterojunction on the characteristics of the diodes wer e studied experimentally and using simulation. The diodes fabricated e xhibited I-V characteristics ideality factors between 1.05 and 1.20.