Analysis of interface states in Pd/n- GaN by temperature and frequency dependent admittance

The measured frequency-dependent ac admittance over a range of temperatures (100 K-300 K) was used to obtain the admittance G_ss + jωC_ss associated with the displacement current in the Pd/GaN interfacial layer. Using two methods based on C-V data at two frequencies and conductance data over a wide range of frequencies, the interface states density is determined to be of the order of 10¹³ cm^-2 eV^-1 at room temperature and shows a slight increase with decreasing temperatures. The derived emission rates range mainly from 10⁵ s^-1 to 10⁶ s^-1 and are to some extent voltage and temperature dependent, showing a decrease with decreasing temperatures. The subsequently obtained capture cross-sections are thermally activated with values varying from 10^-14to 10^-16 cm² and reveal also a significant dependence on the applied forward bias. The density of interface states obtained in the ac regime is roughly in line with that previously derived from the ideality factor of the dc I-V characteristics.