Annealing and Measurement Temperature Dependence of W_(2)B- and W_(2)B_(5)-Based Rectifying Contacts to p-GaN

摘要

Schottky contact formation on p-GaN using W_(2)B/Pt/Au and W_(2)B_(5)/Pt/Aumetallization schemes was investigated using x-ray photoelectron spectroscopy (XPS), current-voltage (I-V), and Auger electron spectroscopy measurements. The Schottky barrier height (SBH) determined from XPS is 2.71 eV and 2.87 eV for as-deposited W_(2)B- and W_(2)B_(5)-based contacts, respectively. By comparison, fitting of the I-V curves using the thermionic field emission model gives unphysical SBHs > 4 eV due to the presence of an interfacial layer acting as an additional barrier to carrier transport. Upon annealing to approx600-700 deg C, the diodes show slight deterioration in rectifying behavior due to the onset of metallurgical reactions with the GaN. The experimental dependence of the reverse leakage current on bias and measurement temperature is inconsistent with both thermionic emission and thermionic field emission models, suggesting that leakage must originate from other mechanisms such as surface leakage or generation in the depletion layer through deep-level defects.