| In the last few years there have been great efforts to research and implement GaN, AlN, and other wurtzite lattice structure III-V semiconductors in high power RF integrated circuits. With their large band gaps and consequently high breakdown voltages, devices made with these materials have the potential to carry larger amounts of power at greater efficiency than current devices designed with GaAs, InP, and other cubic lattice structure III-V and II-VI semiconductors. But because of their wurtzite structure, these III-V semiconductors behave differently than those with cubic lattices, with the major difference being the dipole nature of the lattice leading to spontaneous and piezoelectric induced electric fields. These must be taken into account when designing and modeling, designing, and manufacturing heterojunction devices made with these materials.; When a heterojunction of nominally doped AlN or AlGaN and GaN is formed, the lattice mismatch induces a spontaneous electric field and a mechanical strain induced piezoelectric field, which orient either in the same or opposite directions. With sufficient strength these fields can create a notch in the conduction band edge at the interface, resulting in the formation of a 2deg electron sheet on the GaN side of the junction. This 2deg electron gas can form the effective channel of an AlGaN/GaN HFET, even in nominally undoped material, as they are present in concentrations on the order of 10 12 cm-2 and greater.; The previous version of BandProf software created by Dr. Bill Frensley is a fully functioning analysis tool for aiding in the design of solid state devices composed of materials with cubic or zinc-blend lattice structures (i.e. Si, GaAs, InP, etc.). This includes a band profiling tool, 2D and 3D charge calculators, C(V) modeling, and quantum states analysis. The additional programming adds new data structures to BandProf as well as a few modifications to parts of the previous version so that the program can now fully function with strained materials of the wurtzite lattice structure as well as those with cubic lattices. |
