Hf-Based and Zr-Based Charge Trapping Layer Engineering for E-Mode GaN MIS-HEMT Using Ferroelectric Charge Trap Gate Stack

Abstract

E-mode hybrid ferroelectric charge storage gate (FEG) GaN HEMTs have shown promising performances for future power GaN device applications. The FEG-HEMT demonstrates a combination of ferroelectric polarization and charge trapping process in the ferro-charge-storage gate stack, leading to a positive threshold voltage shift for E-mode operations. In this work, FEG-HEMTs with various Hf-based and Zr-based charge trapping layers are systematically studied. FEG-HEMT which employed nitrogen incorporated HfO2 (HfON) as the charge trapping layer shows an E-mode operation with the highest $V_{\mathrm{ th}}$ (+2.3 V) after initialization. Moreover, the gate leakage of the HfON sample was further reduced due to the nitrogen incorporation, leading to a more complete charging process during initialization. The $V_{\mathrm{ th}}$ instability is also addressed and investigated. The FEG-HEMT with HfON as the charge trapping layer showed a negligible $V_{\mathrm{ th}}$ hysteresis (−43mV) and the highest $V_{\mathrm{ th}}$ stability in both the PBTI (positive bias threshold voltage instability) and NBTI (negative bias threshold voltage instability) test measurements.

Keywords

• AlGaN/GaN
• metal-insulator-semiconductor (MIS)-HEMT
• enhancement-mode
• charge trap gate stack
• threshold voltage stability