In the following, a classification of device performance degeneration mechanisms is listed for III-V HEMTs from recent publications. The limitations can first be distinguished between reversible and non-reversible effects. For the reversible effects another distinction is made between thermal and electrical. The thermal limitations can be separated from the electrical ones by comparing the dissipated DC power.
Reversible effects are:
Non-reversible effects are:
Other non-reversible mechanisms are:
The thermal and electrical mechanisms are naturally combined, e.g. by the lattice temperature dependence of the impact ionization rates and the rise of .
Due to the observation of the previous section, a third group is named process enhanced failure mechanisms. This group is the most undesirable, yet, the most interesting, since it leads to a more complete understanding of the fabrication technology. Suggested mechanisms are:
Investigations of the physical background of the changes at the metal-semiconductor Schottky interface mostly named "gate-sinking" have been recently performed. The naming arises from the similarity to an effective reduction of at the nanometer scale. Generally, non-reversible increased interdiffusion is assumed to be the origin . An explanation of a similar reversible effect is reported by Blanchard et al. in .
Thus, most of the non-reversible and process enhanced failure mechanisms are related to the metal-semiconductor or semiconductor-SiN interface.