Transport in III-Nitride Devices

Carrier and thermal transport in semiconductors – both important parameters for the operation of electronic and optoelectronic devices – are primarily dependent on the thermal conductivity of the crystal lattice. Dominant anharmonic coupling processes, such as electron-phonon and phonon-phonon coupling, provide helpful insights into the thermal characteristics of wide bandgap semiconductors. Investigation on phonon coupling mechanisms will expand our understanding of their effects on electron transport and thermal conductivity of semiconductor devices, whereby mitigate the associated device problems and finally improve the performance of electronic and optoelectronic devices. More specifically, in high electron mobility transistors (HEMTs), the fast emission of longitudinal optical (LO) phonons can result in the formation of hot spots near the gate region where high electric fields produce hot electrons. In this thesis, we investigate the probability of phonon emission as a function of electron energy for confined and interface phonon modes for different wurtzite heterostructures. Novel phonon engineering concepts are introduced which facilitate thermal management through the production of polar optical phonons and acoustic phonons. This work offers a wide range of theoretical modeling and experimental studies of the carrier and thermal transport dynamics in structures including those in GaN- and AlN-based devices.