Measurement of piezoelectrically induced charge in GaN/AlGaN heterostructure field-effect transistors

Electron concentration profiles have been obtained for AlxGa1-xN/GaN heterostructure field-effect transistor structures. Analysis of the measured electron distributions demonstrates the influence of piezoelectric effects in coherently strained layers on III-V nitride heterostructure device characteristics. Characterization of a nominally undoped Al0.15Ga0.85N/GaN transistor structure reveals the presence of a high sheet carrier density in the GaN channel which may be explained as a consequence of piezoelectrically induced charges present at the Al0.15Ga0.85N/GaN interface. Measurements performed on an Al0.15Ga0.85N/GaN transistor structure with a buried Al0.15Ga0.85N isolation layer indicate a reduction in electron sheet concentration in the transistor channel and accumulation of carriers below the Al0.15Ga0.85N isolation layer, both of which are attributable to piezoelectric effects. (C) 1997 American Institute of Physics. [S0003-6951(97)01245-X].