Disclosed is a Group III nitride semiconductor device comprising a stress-absorbing layer having: an amorphous silicon nitride layer, an aluminum interlayer, an amorphous aluminum nitride pre-layer and a polycrystalline Group III nitride layer containing aluminum. The pump unit incorporates a hydraulic pump having a pump shaft. A set of time frequency codes is defined, wherein each code specifies one of a plurality of unique band versus time sequences for a particular band group, for sequential data symbols of a given piconet.