A quantitative approach for trap analysis between Al0.25Ga0.75N and GaN in high electron mobility transistors
Walid Amir, Ju‐Won Shin, Ki‐Yong Shin, Jae‐Moo Kim, Chu‐Young Cho, Kyungho Park, Takuya Hoshi, Takuya Tsutsumi, Hiroki Sugiyama, Hideaki Matsuzaki, Tae‐Woo Kim
Abstract
Abstract The characteristics of traps between the Al 0.25 Ga 0.75 N barrier and the GaN channel layer in a high-electron-mobility-transistors (HEMTs) were investigated. The interface traps at the Al 0.25 Ga 0.75 N/GaN interface as well as the border traps were experimentally analyzed because the Al 0.25 Ga 0.75 N barrier layer functions as a dielectric owing to its high dielectric constant. The interface trap density D it and border trap density N bt were extracted from a long-channel field-effect transistor (FET), conventionally known as a FATFET structure, via frequency-dependent capacitance–voltage (C–V) and conductance–voltage (G–V) measurements. The minimum D it value extracted by the conventional conductance method was 2.5 × 10 12 cm −2 ·eV −1 , which agreed well with the actual transistor subthreshold swing of around 142 mV·dec −1 . The border trap density N bt was also extracted from the frequency-dependent C–V characteristics using the distributed circuit model, and the extracted value was 1.5 × 10 19 cm −3 ·eV −1 . Low-frequency (1/ f ) noise measurement provided a clearer picture of the trapping–detrapping phenomena in the Al 0.25 Ga 0.75 N layer. The value of the border trap density extracted using the carrier-number-fluctuation (CNF) model was 1.3 × 10 19 cm −3 ·eV −1 , which is of a similar level to the extracted value from the distributed circuit model.