Substrate-Coupled Cross-Talk Effects on an AlGaN/GaN-on-Si Smart Power IC Platform

Cross talks between low-voltage peripheral devices and high-voltage (HV) power devices on an AlGaN/GaN-on-Si smart power IC platform are investigated by monitoring the transfer, output, and transient characteristics of a low-voltage AlGaN/GaN high-electron mobility transistor (HEMT) with an HV bias stress applied to an adjacent isolated electrode. The electric measurement was conducted under two types of substrate termination, i.e., floating and grounded. The substrate termination is shown to be the critical factor in the cross talk. The low-voltage HEMT exhibits significant drain-current degradation with a floating substrate, but remains stable with a grounded substrate. It is determined that a coupling path of the switched HV stress is formed from the HV node to the floating low-resistivity Si substrate, and then from the substrate to the HEMT. The negative net charges in the GaN buffer are caused by the electrons injected from the 2DEG channel. It is found that a grounded substrate is helpful for eliminating the cross-talk effect.