An Improved Approach for an Intermediate Measurement Routine of Dynamic On-State Resistance for GaN Power Devices

Inhalt:
The dynamic on-state resistance RDS,on is one key challenge for GaN (Gallium Nitride) power devices. In this article, a practical readout routine for the assessment of the dynamic on-state resistance in commercially available GaN technologies is presented. The preconditioning performed in off-state and the drain bias VDS,q and timing toff in particular has a decisive role on the behaviour of the RDS,on. The application of a pulsed I-V operation (soft-switching) routine enables very precise control of the preconditioning state, a large number of repetitive pulses without high power losses and is hardly susceptible even for larger parasitic inductances. Preconditioning timings of 1 to 100 ms are aspired due to device technology reasons and the efficient utilization of the test equipment. This is similar to the routine of measuring the threshold voltage hysteresis in SiC MOSFETs. The presented test setup enables separate biasing of the drain voltage (>650 V) or gate bias (zero/negative) and applying a drain current pulse of > 20 A. Thereby, the methodology can be adapted to devices with low on-resistance or even modules. The method aims for a fast first order assessment of the device and technology as well as for a comparison of static and dynamic RDSon in one setup.