Introspection Into Reliability Aspects in AlGaN/GaN HEMTs With Gate Geometry Modification

Abstract

Reliability enhancement of AlGaN / GaN HEMT is a significant thrust area due to rapidly improving material and processing technology. In this paper, a detailed analysis of gate–shaped AlGaN / GaN HEMT with field plate is presented. Although AlGaN / GaN HEMT with field–plate is well known, its blending with gate–shaping leading to a more robust and reliable behaviour is described in this paper. It is observed that the threshold voltage and transconductance invariably remain constant for various combinations of gate–shaped and field plate placements. The threshold voltage for all the devices are found to be – 5.8 V. The peak transconductance for the devices without field plate and with field plate is $\sim ~0.16$ S/mm and $\sim ~0.15$ S/mm, respectively. Apart from leakage current, the electric field also gets mitigated for both gate–shaped and field–plated devices by $\sim ~45$ % and $\sim ~68$ %, respectively. The moderation in electric field further assists in the reduction of electron temperature for gate–shaped and field–plated structures by $\sim ~12$ % and $\sim ~85$ %, respectively. Additionally, breakdown voltage increases for the gate–shaped devices to 133 V as compared to 120 V of conventional devices without field plate. Significant reduction in leakage current, electric field, and electron temperature is accompanied by a minor increment in capacitance for the field–plated structure, hence, the proposed structure is expected to enhance reliability of the device. Thus, it is anticipated that the proposed devices with enhanced reliability would be a step ahead of conventional devices and would find major applications in high power domain.

Keywords

• Capacitance voltage (CV)
• electron temperature
• GaN HEMT
• gate shape
• leakage current