Changes in the Schottky barrier height of Ni on AlGaN∕GaN heterostructure field effect transistor structures are characterized by internal photoemission spectroscopy (IPE) as a function of pre-metallization processing conditions and postmetallization ultrahigh vacuum annealing. Low energy electron-excited nanoluminescence spectroscopy and mapping reveal AlGaN near band edge emission variations that correlate with IPE Schottky barrier height. Ni∕AlGaN interface impurities measured by secondary ion mass spectrometry are also correlated with IPE Schottky barrier height. We show that changes in the Schottky barrier height and the appearance of dual barriers are dominated by changes in the local Al mole fraction. Interfacial oxygen and carbon have secondary but systematic effects as well.
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Bradley et al. (2005) studied this question.