Date

2019

Author

Boyacı, Lütfi

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In this thesis, the radiation performances of the commercial GaNFETs were investigated for the possible future integration of these devices to the power subsystems of the satellites as a main switching power element instead of the Silicon MOSFET. Two main irradiation tests were applied to the GaNFETs, namely proton irradiation test, and gamma-ray irradiation test. By these tests, tough space radiation environment was simulated to understand the GaNFET’s radiation performances. In the proton irradiation test, it is aimed to investigate the device’s performance of the Single Event Effect (SEE) which is the failure caused by the strike of the single high energetic particle. A GaNFET EPC2034 (200V, 48A) from Efficient Power Conversion Corporation (EPC) was chosen as a test sample considering the fact that it could be a possible candidate of the switch for the 100 V space bus designs. Four test samples were positioned on two test cards. They were irradiated with the 30 MeV protons while the devices are switching. A flux of 8.2x109 protons/cm2 /s is applied for 12.5 seconds for both test cards to reach ultimate fluence of 1011 protons/cm2 as declared in ESCC Specification No. 25100. Real-time measurements were taken. Vgs - Ids characteristics are measured and recorded for each device before, during and In this thesis, the radiation performances of the commercial GaNFETs were investigated for the possible future integration of these devices to the power subsystems of the satellites as a main switching power element instead of the Silicon MOSFET. Two main irradiation tests were applied to the GaNFETs, namely proton irradiation test, and gamma-ray irradiation test. By these tests, tough space radiation environment was simulated to understand the GaNFET’s radiation performances. In the proton irradiation test, it is aimed to investigate the device’s performance of the Single Event Effect (SEE) which is the failure caused by the strike of the single high energetic particle. A GaNFET EPC2034 (200V, 48A) from Efficient Power Conversion Corporation (EPC) was chosen as a test sample considering the fact that it could be a possible candidate of the switch for the 100 V space bus designs. Four test samples were positioned on two test cards. They were irradiated with the 30 MeV protons while the devices are switching. A flux of 8.2x109 protons/cm2 /s is applied for 12.5 seconds for both test cards to reach ultimate fluence of 1011 protons/cm2 as declared in ESCC Specification No. 25100. Real-time measurements were taken. Vgs - Ids characteristics are measured and recorded for each device before, during and after irradiation. It is observed that the devices retained their functionally. All the devices remained healthy and continued to operate. No failure was observed. Further irradiation is applied for one of the test cards (having two GaNFETs) with a destructive purpose. Same flux level is applied for 30 minutes up to a total fluence level of 1.476x1013 protons/cm2 which is quite higher level than that of appointed in the ESCC standard. It is observed that the GaNFETs stayed fully functional under this elevated level of radiation and no destructive events and irreversible failures took place for transistors. This study showed that the irradiated GaNFETs are reasonably resistant to applied proton radiation. In the gamma-ray irradiation test, the objective was to investigate the Total Ionizing Dose (TID), which corresponds to the cumulative radiation effect, performance of the devices. Two test samples were chosen, EPC2034 and GS61004B (100 V - 45 A) from GaN Systems, respectively. GS61004B was considered as a possible candidate of switch for the 28 V or 50 V power system buses. Nine irradiation test samples for each brand were assembled to two irradiation boards separately. In each board, three of the devices were biased from gate to source, three of them were biased from drain to source and the remaining three were unbiased to observe the bias effects on the device’s radiation performance. The radiation dose was adjusted to 12,5 kRad (Si)/hour. Measurements were taken for the levels of 12.5, 25, 50 and 100 kRad respectively between the 1, 1, 2, and 4 hours of gamma-ray irradiation intervals. Gate to source voltages, drain to source voltages and drain current waveforms were recorded for the switching periods. Gate to source threshold voltages, gate to source plateau voltages, gate to source rise and fall times, and drain to source rise and fall times were analyzed for each device under test in detail. All the 18 devices stayed healthy and fully operational. No irreversible or destructive effects were observed. No meaningful or one-way change was noticed on the devices’ gate to source threshold voltages and plateau voltages or rise and fall times. Characteristics and the performances of the devices have not changed. It was clearly observed that the irradiated samples were radiation-resistant up to a total dose level of 100 kRad regardless of the bias condition.

Subject Keywords

Protons., Keywords: GaNFETs, Proton Irradiation Test, Gamma Irradiation Test, Single Event Effect (SEE), Total Ionizing Dose (TID).

URI

http://etd.lib.metu.edu.tr/upload/12624501/index.pdf
https://hdl.handle.net/11511/44164

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Graduate School of Natural and Applied Sciences, Thesis