A novel approach is proposed to enhance heat dissipation and reliability in high electron mobility transistors based on wide bandgap semiconductor materials. The approach consists in by incorporating a backside gate, through the Si substrate, directly under the top side gate finger. Heat generated within the active area of the device would be effectively dissipated through the back-side contact. The successful fabrication of the backside gated device would produce more reliable power transistors with higher drain breakdown voltages which could be used as small package and uncooled dc to ac convertors for automotive and solar cell applications. From an educational prospective, this project will provide training for both graduate and undergraduate students. Special efforts will be made to recruit female and underrepresented minority students for participation. Research discoveries from this project will be incorporated into the semiconductor materials and processing course developed by the principle investigator. Outreach activities supported by the University of Florida, including school visits, the training of high school senior students, and participation in the NSF GK-12 Program, will be conducted along with the proposed research work.
Gallium nitride (GaN) material based high electron mobility transistor (HEMT) based structures have shown great potential for high voltage (>1000V) and high power density applications (>15 W/mm). This includes high efficiency uncooled dc to ac convertors for electrical cars and solar cells due to its superior electron mobility and saturation, as well as, its energy bandgap of 3.3 eV as compared to 1.12 eV for silicon (Si). However, the current device performance is limited by the high junction temperature due to inefficient heat dissipation of the device design. Higher junction temperatures not only degrade HEMT dc and rf performance, but also diminish the device reliability. Thus, it is very critical to effectively dissipate heat generated during device operation for high power electronics. By taking advantage of GaN HEMT structures grown on SiC or Si substrate, the PI intends to place a through substrate via hole directly underneath the active area of the HEMT and fill up the via hole with plated copper. Not only can the heat generated within the active area of the device be effectively dissipated from this via hole, the back-side via contact itself also can be used as a field plate or a back gate to further increase the device operation voltage.
