【Member News】The Paper by the Team of Academician Hao Yue of Xidian University was Selected in ISPSD 2023 —— An Electro-Thermal Co-Designed Ga₂O₃ [100] Trench Power Diode Featuring Ferroelectric Dielectric

The first author of the paper is Associate Professor Li Yuan, and the corresponding author is Academician Hao Yue

Purpose of Work
      One major roadblock toward the maturation of Ga₂O₃ technology is device overheating. Although with the higher k_T[010] of [100] trench sidewall compared to [010] trench sidewall, the Ga₂O₃ trench devices with [100] trench are rarely adopted, due to the worst sidewall interface quality induced by sidewall-orientation-dependent etch damage, even after the wet etch repair using acids1-2. Optimized sidewall interface quality (OSIQ) of the trench is not only preferred, but also urgently necessary for comprehensive improvement of electro-thermal performance of Ga₂O₃ trench device.
Approach
      A new interface-quality optimization strategy based on ferroelectric dielectric -PZT is presented in this study for the first time. Ga₂O₃ trench diode of [010] trench (0°rotation) and [100] trench (90°rotation) with HfO₂ (TD1) and PZT (TD2&3) are fabricated respectively (Fig.1-4). Different from the limited success of using wet etch repairing technique, when a forward voltage is applied on the anode, the built-in electric field induced by the polarization of PZT is proven to effectively alleviate the negative charge trapping near the sidewall of the trench. Moreover, when self-heating happens, due to the higher k_T[010], whether from the current level under IV measurement or the junction temperature under the same forward power consumption, the OSIQ [100] TD2&3 exhibit better performance compared with [010] TDs.
Results and Significance
      1) TD1 group (HfO₂)-worse IV but lower junction temperature of [100]: ⅰ) 90°rotation TD1 shows lower current compared with 0°rotation in both pulsed (trapping effect³) and DC measurement (self-heating effect³) (Fig.5). ⅱ) 90°rotation TD1 shows the lower junction temperature (TTI measurement4)
compared with 0°rotation TD1 under the identical power consumption (Fig.6).
      2) TD2&3 group (PZT)-better IV and lower junction temperature of [100]: ⅰ) OSIQ 90°rotation TD2&3 show higher current compared with 0°rotation in both pulsed and DC measurement (Fig.7&8&10).The OSIQ and higher k_T[010] jointly contribute to this. ⅱ) Higher current under downward pulse condition than that of upward pulse between 3V and 11V (Fig.7(a), (b)) and the difference between downward sweep and upward sweep suggest that the negative charge trapping condition of the sidewall is improved for TD2&3, but it is not completely alleviated. A pre-voltage stress is cautiously given to TD2 with 0° & 90°(15V&16V) and TD3 with 0° & 90°(15V&16.5V) until downward and upward of pulsed2 just overlaps (Fig.7(c), (d)), and TD2&3 show the higher current density under pulsed2 than that of pulsed1(Fig.9), which indicate OSIQ. ⅲ) OSIQ 90°rotation TD2&3 show the lower junction temperature compared with OSIQ 0° rotation group under the identical power consumption (Fig.11&12). Especially, since the current-sharing effect is assumed to becomes significant with the increasing number of trenches, TD2 90°rotation shows the lowest center temperature, which is 9 degree lower than that of TD3 0°rotation.
      For the first time, the presented electro-thermal co-designed Ga₂O₃ [100]TD, featuring ferroelectric dielectric, exhibits better performance compared with [010]TD, which provides great potential for design optimization of Ga₂O₃ trench devices.