Studies of Hot-Electron Degradation in GaN HEMTs with Varying Gate Recess Depths

Hot-electron injection experiments were performed on Al_0.2 GaN_0.8/GaN HEMTs with different gate recess depths formed by reactive ion etching. Flicker noise measured from the devices indicate systematic increase in S_v(f) for devices with increasing recess depths. Furthermore, when the devices were subjected to high dc voltage stress across the conduction channel, the devices with large gate recess were found to exhibit much more significant increase in S_v(f) compared to the control device with no gate recess. Since S_v(f) is directly proportional to the trap density at the AlGaN/GaN heterointerface, the experimental data clearly show that the reactive ion etching process has led to significant degradation in the integrity of the device