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Failure analysis of gan hemt

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govardhanamma

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Please help,
we have tested a 100w gan hemt by applying only gate voltage less than pinch off voltage with out drain voltage, its base is grounded, by giving -5v to gate of pa gate voltage immediatly dropped and it showed some gate current and we have checked continuity of the pcb in resistance mode it is showing short between drain &ground &also gate &ground ,before placing the device we have checked the pcb it is ok but after mounting the device we are facing problem ,please help how to ensure our device is gone or not????????????????????????
 

Remove the part and check resistance from gate to source and gate to drain, both should be high impedance (it's a FET, so there's a highly-resistive oxide layer between the gate metal and the semiconductor). If the resistances are low, your part is dead.

As for shorting on the board, the leads of your part, or the solder on the leads of the part, might be shorting it to the PCB or chassis (depending on the type of device and how it mounts).
 
yes base is grounded

---------- Post added at 01:15 ---------- Previous post was at 01:09 ----------

thanks for ur advice, my device consists of two mosfets in pushpull configuration in flange package,i have to check after removing the device from board ah????????????
 

Yes, I agree, remove the part from the board and check to see if the short went away. Although these are rugged devices, I would still caution to use antistatic handling and gear (especially the soldering iron used!).

If the board is open circuit with the fet removed, and short circuit with the fet installed, and if there are no observable solder balls or other mechanical short circuit, it is probably blown out. But to tell for sure put a small drain voltage on the drain, when the gat is at -5 V, and reduce the gate bias, and see if the drain current goes up. If it does, the fet might not be blown up after all.
 
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