Deep-Level Characterization of n-GaN Epitaxial Layers Using Transparent Conductive Polyaniline Schottky Contacts

摘要

We have successfully investigated surface-related deep levels in n-GaN epilayers with high carrier concentrations by using transparent conductive polyaniline Schottky contacts. High quality Schottky barrier diodes fabricated showed a typical capacitance dispersion phenomenon at ～10 kHz, which is characteristic of conductive polyaniline films with polarization capacitance and resistance components. Steady-state photocapacitance spectroscopy measurements at over this cutoff frequency revealed five photoemission states with their onsets at～1.40, ～1.70,～2.08,～2.64, and ～2.90eV below the conduction band, being identical with the deep levels commonly observed in GaN and AlGaN/GaN. Particularly, the concentrations of the ～1.70 and ～2.90 eV levels were found to increase significantly with decreasing their probing depth range to the near-surface region of the n-GaN layers. Therefore, these levels are probably subject to the surface conditions of the n-GaN layers.