Electrical and Small-Signal Characteristics Degradation of RF GaN HEMTs Under Repetitive ESD Stresses

Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) are widely applied in the radio frequency (RF) power amplifier of the wireless communication field because of superior features. With the massive applications of RF GaN HEMT, the reliability challenges, accompanied with the electrostatic discharge (ESD) issues, are paying increasing attention. The electrical and small-signal characteristics degradation after the repetitive ESD stresses for the RF GaN HEMT have been investigated in this work. It is found that the Schottky gate of the device is damaged after the ESD stresses. These damages induce the shift of pinchoff voltage and the current reduction. However, the damage mechanisms are different for the following two ESD stress scenarios. The Schottky gate of the device zapped on the gate is damaged by the high current density and that of the device zapped on the drain is damaged by the high electric field. Meanwhile, the discharge current can induce traps in the buffer region, which causes the drain current to decrease further. In addition, the S-parameters are measured before and after the ESD stresses. Based on the small-signal equivalent circuit, the main intrinsic elements of the device, including capacitance, inductance, and resistance, have been extracted and analyzed. The results show that the gate-dependent parameters
${C} _{\text {gs}}$
,
${R} _{\text {gs}}$
, and
${g} _{\text {m}}$
, and the drain-dependent parameters
${C} _{\text {ds}}$
and
${G} _{\text {ds}}$
are changed by the ESD stresses due to the damages in the gate and buffer regions.