Terahertz Generation in GaN/AlGaN Superlattices

摘要

Nitride semiconductors based heterostructures have so far been exploited for electronic devices utilizing transport parallel to heterointerfaces. However, the vertical transport and its understanding in this heterostructure system are nascent. Heterojunction bipolar transistors have fundamental problems having to do with low base p-doping in terms of bipolar transistor standards and inferior emitter quality because of the poor quality Mg doped underlying base layer. The PnP variety is even worse. In terms of unipolar vertical transport structures, double barrier resonant tunneling structures have been reported. However, a closer investigation uncovered fundamental problems with reports in that the negative differential resistance so observed was found to be time dependent and number of sweeps. If the observed phenomenon were to be due to resonant enhanced tunneling none of the above should be associated with it, except some hysteresis.