I read that galium nitride and silicon carbide are piezo materials.Does this cause some problems? I can imagine that unwanted piezoelectricity directly in the circuit path would cause some kind of distortion or noise.
Can this be modeled as some kind of parasitic voltage source?
How strong is this effect? I know some piezoelectric materials are alot more piezoelectric than others,is SiC and GaN only extremly weak piezoelectric materials ,so weak that it can be ignored?
Best Answer
I imagine the actual answer may depend on the transistors you're interested in.
For example, there's no "oxide layer" in a typical GaN-on-SiC HEMT; the gate forms a Schottky contact and the device is a "planar" device with a 2DEG. Piezoelectricity has little effect here since there is little potential across the crystal (only along the surface). Incidentally, typical SiC substrates are semi-insulating, so there's no electrical contact on the back-side of the GaN, either. Without the second electrical contact, you won't get any piezo-related effects.