The effect of negative substrate bias on the electrical characteristics of InAlN/GaN MIS-HEMTs

The effect of the negative substrate bias (V _sub) on the device performance of the InAlN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) is studied. When the V _sub decreased from 0 V to  −40 V, the two-dimensional electron gas (2DEG) electron density (n _2D) under the gate region decreased, while the 2DEG electron mobility (µ _2DEG) under the gate region was significantly improved. Due to the InGaN back barrier layer and the thin GaN channel layer (15 nm), the 2DEG electrons in the channel are injected into the InGaN back barrier layer with negative V _sub, leading to the decreased n _2D. The decrease of the n _2D caused the decrease of the collision probability between the polar optical phonon (POP) and the 2DEG electrons, and the enlarged distance between the 2DEG electrons and the AlN/GaN interface, resulting in the weaker POP and interface roughness scatterings and higher µ _2DEG. This provides a possible way to increase 2DEG electron mobility and further improve the device performance of InAlN/GaN MIS-HEMTs. (paper)