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  • Bikinin br Selection of ions for GaN Systems sample test Sam


    Selection of ions for GaN Systems sample test Sample construction analyses has been provided to analyze the beam penetration of several ions of the cocktail in the component. An X-ray and optical view of GaN System devices parts is presented at Fig. 5, Fig. 6 respectively. The drain and source electrodes (respectively top and bottom) are separated by a “spring” without metal. This uncovered area was directly exposed to the radiation rays. The SRIM analysis provides the following results:
    Identified failures During the irradiation, LET is set at 16.1 MeV/(mg/cm2) with range of 49 μm. Table 2 summarizes the main conditions used during heavy Bikinin tests. Fig. 7 provides an acquisition of the destructive event recorded on a TDS3054B oscilloscope. The observed transient has very large amplitude higher than the resolution defined. The amplitude of the event is expected larger than 100.V peak to peak and about 350 ns wide. During run 3, several SETs events were triggered on the monitoring. However, these events were not destructive and categorized as SETs events (see Fig. 8). In fact, the components were still functional after these events. The following run has exhibited a destructive failure during the beginning of the run 4 (t = 3) which has conducted to the loss of the component (see Fig. 9). (This indicates that there is room for improvements in the test circuit; it has been well tested on Si components but not yet on GaN components). The associated cross-section has been calculated as 0.16% of the active surface. The associated safe operating area can be determined between 550 V and 650 V for the nickel ion. It is relatively high compared to maximum recommended voltage. The cross-section of sensitivity is small compared to total sample surface. Fig. 10 shows that important damages are observed in metal lines (mainly M2 & M3) and dielectric layers. Short between Source (M2) and Drain (M3) are visible on cut3 and the damages are also visible in the reference area (M2 layer). On the other side, no abnormality was detected in the active area (M1 contacts) of 3 cuts. Therefore, the origin of the destructive event associated to run 4 failures is the dielectric rupture in the intermetallic region between source and drain as shown in Fig. 11. The scenario that could be provided by these results is close to that proposed in our previous work based on TCAD simulations [8], it has been observed that susceptible region which may lead to the dielectric rupture can be located at the field plate edge. The source field plate contact in the intermetallic region (M2) is the nearest to the drain contact (M3) and creates the highest electrical stress which can exceed the edge gate stress on the drain side. Therefore, impact ionization mechanism and related multiplication phenomena are enhanced when a heavy ion strikes under the field plate edge rather than the other track positions as shown in Fig. 12, that compare the two critical positions, gate and field plate. Wrobel suggested that the density of electron-hole plasma along the heavy ion track in the dielectric induces a conductive “pipe” that can be a discharge path of energy stored on the capacitor [9]. We suppose that this hypothesis is possible in this case when heavy ions strike in the near the source field plate contact in the intermetallic region (M2).
    Preliminary study of PANASONIC PGA26 Concerning the SOA of normally-off GaN/AlGaN HEMTs we used Panasonic PGA26 components with energetic ions (Rh and Xe) to cover space environments. The devices were polarized in the off state (Vgs = 0 V) but at more negative voltages as well (−3 V, −6 V and − 9 V). Before and after each irradiation threshold voltage and Gate voltage ramp characteristics of the devices are measured for evaluating the damage induced by the irradiation. At least 3 passed device were tested for each experiment under the same conditions for a given SOA point. During this test only one destructive event was triggered on the monitoring. This damage is very similar to the gate rupture (SEGR) in MOSFET and is shown by the sudden increase of the gate and drain current leakage as shown in Fig. 13. Fig. 14 shows that the associated safe operating area of Panasonic PGA26 for the Rh and Xe ion and for different Vgs polarisations, it can be determined at 300 V (50% of Vbr) for Vgs = −9 V and 325 V (54% of Vbr) for Vgs = 0 V.