2DEG behavior of AlGaN/GaN HEMTs on various transition buffers

We are reporting the 2DEG mobility and sheet carrier concentration behavior of AlGaN/GaN HEMT stacks that are grown on different kinds of transitions from AlN buffer to epi-GaN. The role of each transition in terms of interfacial roughness and epi-GaN crystallinity are discussed. Further, the observed material parameters are correlated with the HEMT 2DEG property. Enhancement in 2DEG mobility was observed from the stacks those exhibit low surface roughness irrespective of the scattering seen in HRXRD FWHMs. This results show that other than the dislocation reduction and crack free film, the low surface roughness is essential for a better confinement of 2DEG and an optimum carrier concentration.