Current conduction in an implant isolated GaAs/AlGaAs heterostructure

We report the current-voltage characteristics of an oxygen implant-isolated region of a GaAs/AlGaAs heterostructure between 25 and 295 K. Current conduction was dominated by bulk rather than metal contact limited effects. Bulk conduction in the implant-isolated region is due to several different mechanisms; at low electric fields a resistive current; at low temperatures and high electric fields, field ionization current proportional to V2 exp(−V0/V); and at high temperatures and high electric fields, Poole–Frenkel conduction proportional to V exp(aV1/2/rkT−qφb/rkT). The resistive current can further be separated into two components, one of which dominates at low temperatures and is proportional to V exp(−B/T1/4), and the other which dominates at high temperatures and is proportional to V exp(−Ea/kT). These results are applicable to any GaAs-based structure rendered semi-insulating by an isolation implant, and describe the current conduction characteristics from zero bias to breakdown. Such a description is critical to understanding leakage currents in GaAs/AlGaAs devices such as high-performance heterojunction bipolar transistors, field-effect transistors, and laser diodes that commonly employ implant isolation as a part of the fabrication process.