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The Schottky barrier characteristics of Ni on p-GaN have been investigated using current–voltage–temperature (I–V–T) and capacitance–voltage characteristics (C–V) measurements. Barrier height values ranging from 2.68 to 2.87 eV were obtained from C–V measurements. The temperature dependence of I–V characteristics clearly indicated the dominance of tunneling current in the transport mechanism of the diodes, therefore, barrier height determination using I–V measurements can lead to erroneous results, as indicated by the wide range of barrier heights reported in the literature. Acceptor concentration, deduced from C–V measurements, was found to be of 10[sup 19]/cm[sup 3] within 200 Å of the sample surface, and tapered off to be ∼10[sup 18]/cm[sup 3]. These values are 10–100 times higher than the hole concentration of ∼10[sup 17]/cm[sup 3] obtained from Hall measurements. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The internal photoemission method was used to measure the Schottky barrier height of Ni on AlGaN/GaN heterostructures. A barrier height of 1.31 eV was found for the Ni/Al[sub 0.15]Ga[sub 0.85]N/GaN heterojunction structure, as compared to a barrier height of 1.28 and 1.02 eV for the Ni/Al[sub 0.15]Ga[sub 0.85]N and Ni/GaN Schottky diodes, respectively. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A method for enhancing effective Schottky barrier heights in III–V nitride heterostructures based on the piezoelectric effect is proposed, demonstrated, and analyzed. Two-layer GaN/Al[sub x]Ga[sub 1-x]N barriers within heterostructure field-effect transistor epitaxial layer structures are shown to possess significantly larger effective barrier heights than those for Al[sub x]Ga[sub 1-x]N, and the influence of composition, doping, and layer thicknesses is assessed. A GaN/Al[sub 0.25]Ga[sub 0.75]N barrier structure optimized for heterojunction field-effect transistors is shown to yield a barrier height enhancement of 0.37 V over that for Al[sub 0.25]Ga[sub 0.75]N. Corresponding reductions in forward-bias current and reverse-bias leakage are observed in current–voltage measurements performed on Schottky diodes. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]