In order to clarify the effect of charged dislocations and surface donor states on the transport mechanisms in polar AlInN/AlN/GaN heterostructures, we have studied the current-voltage characteristics of Schottky junctions fabricated on AlInN/AlN/GaN heterostructures. The reverse-bias leakage current behaviour has been interpreted with a Poole-Frenkel emission of electrons from trap states near the metal-semiconductor junction to dislocation induced states. The variation of the Schottky barrier height as a function of the AlN layer thickness has been measured and discussed, considering the role of the surface states in the formation of the two dimensional electron gas at AlN/GaN interface.
The pH response of GaN/AlInN/AlN/GaN ion-sensitive field effect transistor (ISFET) on Si substrates has been characterized. We analyzed the variation of the surface potential (AV sp /ApH) and current (A/ ds /ApH) with solution pH in devices with the same indium content (17%, in-plane lattice-matched to GaN) and different AlInN thickness (6 nm and 10 nm), and compared with the literature. The shrinkage of the barrier, that has the effect to increase the transconductance of the device, makes the 2-dimensional electron density (2DEG) at the interface very sensitive to changes in the surface.Although the surface potential sensitivity to pH is similar in the two devices, the current change with pH (A/ds/ApH), when biasing the ISFET by a Ag/AgCl reference electrode, is almost 50% higher in the device with 6nm AlInN barrier, compared to the device with lOnm barrier. When measuring the current response (A/ ds /ApH) without reference electrode, the device with thinner AlInN layer has a larger response than the thicker one, of a factor of 140%, and that current response without reference electrode is only 22% lower than its maximum response obtained using reference electrode.
International audienceBulk conduction in molecular beam epitaxial InN layers has been confirmed using low frequency noise measurements versus temperature. A generation-recombination process has been identified at low temperatures 100 K and attributed to a trap with a discrete energy level in the band gap. The energy position of this trap has been determined to be around 52 meV below the conduction band minimum
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