Substrate Management for GaN Bi-directional Switch Based on Charge Recycling of Slow Recovery Diode

We demonstrate a substrate management circuit for GaN-on-Si bi-directional switches (BDS) that delivers effective suppression of the detrimental back-gating effect, e.g. dynamic on-resistance degradation. The circuit features two low-cost Si slow recovery diodes (SRD) in back-to-back configuration between the two sources of the BDS, in conjunction with an area-efficient on-chip self-biased GaN-HEMT substrate stabilizing network. The new substrate management solution enables a wide operating frequency range and high voltage slew rates (dv/dt). The SRDs, with their anodes connected to the Si substrate, are able to clamp the potential of the substrate of GaN BDS by storing holes flowing out from the substrate (when forward biased) and provide a reverse hole current flowing back to the substrate (when reverse biased) to compensate the negative charges remaining in the substrate, functioning as hole recycling components. The back-to-back SRDs also equip the GaN BDS with bidirectional avalanche breakdown capability. The GaN-HEMT substrate stabilizing networks feature auxiliary GaN transistors that can supply additional charges to the substrate to compensate any charge imbalance during switching transients, thereby stabilizing the substrate by eliminating the residual substrate voltage.