Abstract
Vertical electronic transport in periodic GaN/AlGaN multiple-quantum-well structures grown on free-standing GaN substrates is investigated. Highly nonlinear current-voltage characteristics are measured, displaying a clear transition from a high-resistance state near zero applied bias to a low-resistance state as the voltage is increased. The measurement results, including their temperature dependence and the variations in turn-on voltage with subband structure and bias polarity are in full agreement with a picture of sequential tunneling through the ground-state subbands of adjacent coupled quantum wells. Scattering-assisted tunneling due to interface roughness or structural defects appears to be the dominant transport mechanism. The potential role of photon-assisted tunneling is also investigated.
Published Version
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