In the last few years, the development and technological expansion in sectors such as electric mobility, renewable energies, and telecommunications have led to a constant increase in the demand for energy worldwide. Energy conversion systems, such as DC-DC converters, rectifiers and inverters are the core of every electronic device, as they provide the adequate power management. Most of the devices currently on the market are based on Silicon, a semiconductor material that, starting from the first demonstration by John Bardeen, William Shockley and Walter Brattain at Bell Labs 75 years ago (in 1948), has enabled the significant technological development that we all know. However, it is commonly believed that Silicon has reached its physical limit and is insufficient to guarantee the power and efficiency required for the development of future electronic applications, especially in the fields mentioned above where a large amount of power must be managed and converted. It is estimated that the energy lost due to the inefficiency of electronic conversion devices is about 80% of the total energy produced. To overcome the limitations imposed by the "old" technology, new materials have emerged as leading candidates for the next generation of power electronic devices. These are wide band-gap semiconductors, such as Gallium Nitride (GaN) and Silicon Carbide (SiC), which, owing to their outstanding properties, promise the manufacture of devices capable of handling high power densities with minimal energy losses. Therefore, the exploitation of these materials in the electronics field can improve current technologies and be the support for future ones. This thesis is focused on the study of GaN-based power devices; innovative transistors and diodes with vertical structures have been characterized, and main criticalities were deeply analyzed with the aim of understanding and explaining their origin. These architectures have become the subject of research only in recent years, and they promise to fully exploit the properties of wide band-gap semiconductors. Although significant experimental results confirm their enormous potential, several challenges still need to be overcome, especially with regard to fabrication processes, which still need to be refined and investigated for a full control of their operation.
Negli ultimi anni, lo sviluppo e l'espansione tecnologica in settori quali la mobilità elettrica, le energie rinnovabili e le telecomunicazioni hanno portato ad un costante aumento della domanda di energia elettrica in tutto il mondo. I sistemi di conversione dell'energia, quali convertitori DC-DC, AC-DC e inverter, sono il cuore di ogni dispositivo elettronico in quanto provvedono a fornire l'adeguata alimentazione di cui necessitano. La maggior parte dei dispositivi presenti ad oggi in commercio sono basati sul Silicio, un materiale semiconduttore che, a partire dalla prima dimostrazione di John Bardeen, William Shockley e Walter Brattain ottenuta 75 anni fa (nel 1948) nei Laboratori Bell, ha consentito il notevole sviluppo tecnologico che tutti noi conosciamo. Tuttavia, è opinione comune ritenere che il Silicio abbia raggiunto il proprio limite fisico e sia insufficiente a garantire la potenza e l'efficienza adeguata allo sviluppo di future applicazioni elettroniche, specialmente negli ambiti di cui sopra, in cui una gran quantità di energia deve essere gestita e convertita. Si stima infatti che l'energia perduta causa inefficienza degli apparati elettronici di conversione sia circa del 80% sul totale dell'energia prodotta. Per superare i limiti imposti dalla "vecchia" tecnologia, nuovi materiali sono emersi come candidati protagonisti per la nuova generazione di dispositivi elettronici di potenza. Si tratta dei semiconduttori aventi ampio band-gap, come ad esempio il Nitruro di Gallio (GaN) e il Carburo di Silicio (SiC), che con le loro straordinarie proprietà promettono la fabbricazione di dispostivi capaci di gestire alte densità di potenza con perdite di energia minime. Pertanto, lo sfruttamento di questi materiali nel campo dell'elettronica potrà migliorare le attuali tecnologie ed essere di supporto per quelle future. Questa tesi è focalizzata sullo studio di dispostivi di potenza basati sul GaN; innovativi transistor e diodi con strutture verticali sono stati caratterizzati e le principali criticità emerse sono state a fondo analizzate con l’obiettivo di comprenderne e spiegarne l’origine. Si tratta di architetture che solo a partire dagli ultimi anni sono oggetto di ricerca e che promettono un pieno sfruttamento delle proprietà dei semiconduttori ad ampio band-gap. Sebbene importanti risultati sperimentali ne confermino le enormi potenzialità, diverse sfide sono ancora da superare, soprattutto riguardo i processi produttivi atti alla fabbricazione dei dispositivi, ancora da rifinire e investigare per un pieno controllo del loro funzionamento.
Vertical GaN power devices: characterization and instability
DEL FIOL, ANDREA
2022/2023
Abstract
In the last few years, the development and technological expansion in sectors such as electric mobility, renewable energies, and telecommunications have led to a constant increase in the demand for energy worldwide. Energy conversion systems, such as DC-DC converters, rectifiers and inverters are the core of every electronic device, as they provide the adequate power management. Most of the devices currently on the market are based on Silicon, a semiconductor material that, starting from the first demonstration by John Bardeen, William Shockley and Walter Brattain at Bell Labs 75 years ago (in 1948), has enabled the significant technological development that we all know. However, it is commonly believed that Silicon has reached its physical limit and is insufficient to guarantee the power and efficiency required for the development of future electronic applications, especially in the fields mentioned above where a large amount of power must be managed and converted. It is estimated that the energy lost due to the inefficiency of electronic conversion devices is about 80% of the total energy produced. To overcome the limitations imposed by the "old" technology, new materials have emerged as leading candidates for the next generation of power electronic devices. These are wide band-gap semiconductors, such as Gallium Nitride (GaN) and Silicon Carbide (SiC), which, owing to their outstanding properties, promise the manufacture of devices capable of handling high power densities with minimal energy losses. Therefore, the exploitation of these materials in the electronics field can improve current technologies and be the support for future ones. This thesis is focused on the study of GaN-based power devices; innovative transistors and diodes with vertical structures have been characterized, and main criticalities were deeply analyzed with the aim of understanding and explaining their origin. These architectures have become the subject of research only in recent years, and they promise to fully exploit the properties of wide band-gap semiconductors. Although significant experimental results confirm their enormous potential, several challenges still need to be overcome, especially with regard to fabrication processes, which still need to be refined and investigated for a full control of their operation.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/46072