Heterojunction impact avalanche transit-time diodes grown by molecular beam epitaxy

The authors' present the results of a study into the potential benefits of including heterostructures within single-drift impact avalanche transit-time (IMPATT) diodes. One particular heterostructure device, which exploits the change in saturated drift velocity in going from one material to another (the double-velocity avalanche transit-time (DOVATT) diode), is examined in detail using a series of GaAs/Al_xGa_1-xAs devices grown by molecular beam epitaxy. Contrary to claims in the literature, they conclude that there is little prospect for realizing high-performance DOVATT diodes using this materials system. The authors' note, however, that a novel In_xGa_1-xAs heterojunction technique to reduce series resistance appears promising and is deserving of further study.