EST Seminar presents "Oxide Semiconductor Electronics: from BEOL thin film circuits to high-voltage UWBG"
Oxide semiconductors' unique properties – a wide bandgap, reasonably high electron mobility, and ease of bulk and thin film preparation – make them prime material candidates for a variety of electronic devices. In this talk, I will describe my group's recent work on amorphous and crystalline oxide semiconductors for back end of line (BEOL) thin film circuitry and for high-voltage ultra-wide bandgap (UWBG) power devices, respectively. First, we exploit the thermodynamics of interfacialin situredox reactions with amorphous zinc tin oxide (a-ZTO) semiconductor to make MISFETs, MESFETs, Schottky diodes, and resistive memory devices that can be monolithically integrated with silicon CMOS. We demonstrate rectifiers that can harvest RFID wireless power and inverters that are compatible with low voltage silicon ICs. Furthermore, we develop novel, scalable atomic layer deposition processes to realize high-qualitya-ZTO semiconductor films, high-kAl2O3gate insulators and passivation layers, and Al:ZnO source/drain electrodes. Combining an innovative electro-hydro-dynamic jetting process with additive and subtractive selective area ALD, we realize thin film transistors with channel lengths below the ink-jet printing limit. I'll also describe our recent work on p-type oxide TFTs using Cu2O, and explain the key challenges in device architecture and materials physics that limit p-TFT performance. Finally, I'll explain how we've taken the learning from thin film oxides and used it to realize ultra-stable ohmic contacts and MOS capacitors to crystalline beta-phase gallium oxide, an ultra-wide bandgap semiconductor of interest for multi-kV power devices.