Electroluminescence Investigation of the Lateral Field Distribution in AlGaN/GaN HEMTs for Power Applications

The lifetime and stability of AlGaN/GaN heterostructure field effect transistors at high power levels can be enhanced by introducing field plates to reduce electric field peaks in the gate-drain region. Simulations of the electric field distribution along the channel using the 2D ATLAS software from Silvaco indicate that above a characteristic drain source voltage three spatially separated electric field peaks appear, one located at the drain-side edge of the gate foot, one at the end of the drain-sided gate field plate, and one at the end of the source shield field plate. The close correlation between lateral electric field and the electroluminescence due to hot electron related intra-band transitions can be very helpful when optimizing the electric field distribution in high power devices. Electroluminescence microscopy images of devices with gate and source shield field plate reveal the peaks located at the locations of enhanced electric field. By studying the voltage dependence of the electroluminescence peaks the influence of the field plates on the electric field distribution in source drain direction can be visualized.