|MIT Department: Electrical Engineering and Computer Science
Faculty Mentor: Tomás Palacios
Undergraduate Institution: Morgan State University
My name is Fadil, I was born and raised in Côte d’Ivoire (Ivory Coast). I am a rising senior majoring in electrical engineering at Morgan State University. My current research interests lie in the area of materials science, mainly semiconductors. I have always been curious about how applied scientists and engineers manage to consistently develop faster, smaller, and more power efficient electronic devices, and this curiosity is what ultimately led me to the interdisciplinary field of materials science. My research experience working on aspects of wide band gap semiconductors such as silicon carbide (SiC), enlightened me on a number of my questions, but also, in a good way, begat more curiosity. Once I clearly identify the challenges that intrigue me the most, I hope to be at the forefront of their resolutions. In my spare time, I enjoy going for a walk in parks, playing the guitar, and listening to debates on contemporary issues.
HIGH TEMPERATURE CHARACTERIZATION of p-GaN Gate AlGaN/GaN HEMTs
Mohamed Fadil Isamotu1, Mengyang Yuan2, Tomas Palacios2
1Department of Electrical and Computer Engineering, Morgan State University
2Department of Electrical Engineering & Computer Science,
Massachusetts Institute of Technology
At high temperatures (over 300°C), conventional semiconductors such as Gallium Arsenide (GaAs) and silicon (Si), are fundamentally limited by their narrow bandgap (1.44 eV and 1.12eV respectively) and high intrinsic carrier density. For most conventional semiconductor-based electronics to operate at temperatures greater than 150 °C, they must be coupled with external cooling systems introducing more weight, complexity, cost, and often noise to the final device. Electronic devices that can reliably operate at such temperatures without cooling mechanism would be beneficial for a wide variety of fields, including, the automotive, aerospace, petroleum, and geothermal industry. Gallium (GaN) as a wide bandgap semiconductor (WBG, 3.4eV), known for its high thermal stability and inert nature, is a promising candidate for high temperature electronics. Moreover, the polarization nature of GaN enables the implementation of AlGaN/GaN HEMTs by forming a high-quality two-dimensional electron gas (2DEG) in the heterojunction. To prove the potential of GaN transistors for high temperature applications, it is critical to characterize the devices at the targeted operating temperatures for an extended period of time.
In this study, we characterized self-aligned normally-off Gate Injection Transistors (GITs, p-GaN Gate AlGaN/GaN HEMTs) with the etch stop process and refractory metal gate, optimized for large scale integration and high temperature operation. 500°C survival tests were first carried out on devices with and without wire bonding pads for over 20 days, and ex-situ measurements were conducted during the test at room temperature to evaluate the devices’ performance, thermal stability of wire bonding, and analyze the potential degradation mechanism for further optimization. The unpadded devices showed improved performances after survival tests, which can be attributed to the improved ohmic contact and gate controllability. On the other hand, the devices with wire bonding pads showed high contact resistance and early velocity saturation due to the degraded connection between bonding pads and ohmic contacts. An automatic platform was then developed for in-situ measurement to monitor the devices’ performance and potential degradation under DC stress at 500°C in real time. The devices showed stable operation at 500°C for over 24h.