Generation of coherent GHz acoustic phonons in AlGaN/GaN microwave field effect transistors

In this paper, the presence of large amplitude GHz coherent phonons in GaN/AlGaN microwave HEMTs, by detecting the phonons using a local reflective optical probe at near normal incidence to active device, tightly focused (1 um) and scanned in the vicinity of the source-gate-drain region. Estimates of the total spatially integrated vibrational energy released from the 2D gas suggests that a possibly significant fraction of the dissipative energy can be released from the HEMT into coherent phonons, providing a potential avenue for bypassing conventional thermal management schemes.