Investigation of AlGaN/GaN HEMT by Post gate annealing and various gate-drain spacing

  • 李 承軒

Student thesis: Master's Thesis


This research proposed the investigation of different gate-drain spacing and different passivation layers on the AlGaN/GaN high electron mobility transistors (HEMTs) We adopt SiO?2 and Al2O3 to be the passivation layers Comparison with different passivation layers we observed that the Stack-passivated HEMTs had better performance We used the atomic force microscopy (AFM) to observe the root mean square (RMS) and the surface roughness We found that the Al2O3 layer had better RMS before and after annealing And we utilized the transmission electron microcopy (TEM) to analyze the oxide thickness The results showed that the oxide layers were approaching the oxide thickness which we designed We also utilized the Electron spectroscopy for chemical analysis (ESCA) to observe that the oxide composition The oxide layer before and after annealing showed that annealing could effectively reduce the traps and the oxygen vacancies Finally we utilized Hall measurement method to confirm the DC characteristics improved The sheet concentration was increased and the electron mobility slightly reduced by passivation layer C-V measurement showed that the k constants hysteresis and interface state density And the results showed that the passivation layers could effectively reduce the traps Post gate annealing was an effectively method to improve performance by repairing the oxide traps and oxygen vacancies The traps decreased made the performance improved The different passivation layer could improve the performance by removing the interface state density and the 2DEG concentration increased And comparison with different passivation layers we found that the stack-passivated layer had the best performance Comparison with different gate-drain spacing we found that the spacing would influence the characteristics 5 ?m spacing the DC characteristics was better but the breakdown was worst 20 ?m spacing the results was opposite with 5 ?m The stack-passivated HEMT had the best performance compared with other passivation layers Combination the different gate-drain spacing different passivation layer and post gate annealing we could obtain the different characteristics And this different characteristics could be applied in different high power applications
Date of Award2015 Jul 31
Original languageEnglish
SupervisorWei-Chou Hsu (Supervisor)

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