Ti- and Fe-related charge transition levels in β−Ga2O3

Abstract

This thesis would not have been possible without the support of many people, and I am eternally grateful for all the support. I hope to see some of you again in the future! The main objective of my PhD project was to study defects in semiconducting oxides within the research project FOXHOUND headed by Prof. Lasse Vines, my main supervisor. I am grateful to Lasse for the opportunity to work on this topic. I have learned much more than I imagined I would when I started. Lasse, you have been a patient and competent supervisor who always took time to answer endless streams of questions. Prof. Truls Norby and Assoc. Prof. Anette Eleonora Gunnaes were co-advisors for my PhD project. I am grateful to Truls for introducing me to the chemist's view on defects and his group FASE/ELCHEM. I am truly sad that I did not get to collaborate more with Anette. I also want to thank Prof. Eduard Monakhov and the late Prof. Bengt Gunnar Svensson. Both were valuable unofficial advisers on my PhD, and helped moving my work along. Most of my work was carried out within the semiconductor physics group at the University of Oslo (LENS), and I would like to thank of all its current and former members for contributing to my work in many ways. There are some people who deserve special thanks. First of all, I am grateful to my long-term office mates Torunn, Sigbjørn and Josef for sharing many conversations and being there for each other. Secondly, I am particularly grateful to all my close collaborators at LENS, and especially Julie, Philip, Ymir, Vegard R., Vegard O., Viktor and Espen. I also want to thank our engineers (Micke, Halvor, Christoph and Viktor) and administrative staff (Marit, Heine and Kristin) for keeping things running! Also, thanks to Ilia, Robert, Vegard R. and Jon for taking care of the needs of the E-Lab and the Online-Setup. I was a co-supervisor for two master students: Vegard R. and Espen. I hope both of them learned something from me, because I did definitely learn from them. I am particularly grateful to Vegard R. for being a large part in building the steady-state photo-capacitance setup used in this work. I also would like to thank all my co-authors from outside of Oslo: Frank from Dresden, Willem, Walter and Danie from Pretoria, Klaus and Zbigniew from Berlin, Antti from Aalto and Joel from California. Special thanks to Willem, Walter and Danie for hosting me in Pretoria and showing me around. Last but not least, I would like to thank my family and my friends for their support!

Defect states and their electric field-enhanced electron thermal emission in heavily Zr-doped β -Ga2O3 crystals

“…agrees well with the E3 in EFG and CZ UID crystals 27 and is likely from native defects since its concentration has been observed to increase after neutron irradiation 40 but we cannot rule out the possibility of Ti origin yet 25 . The signature we observe at 0.86 eV is consistent with E2 which has been attributed to the FeGa 3 + /2 + acceptor charge transition level.…”

Atomic‐Layer‐Ti‐Doped Ga2O3 Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

“…Moreover, at low Ti concentrations, the annealed TGO thin films still show good crystallinity compared with the pure films, where a small number of Ti 4+ substitute Ga atoms at octahedral sites. [ 29,30 ] However, at higher Ti concentrations, the peaks become indistinct indicating the suppression of crystallization. Similar phenomena were observed in TGO films deposited through other methods.…”

Deep-Level Traps Responsible for Persistent Photocurrent in Pulsed-Laser-Deposited β-Ga2O3 Thin Films

“…The Fe trap level of about 0.78 eV energy also behaved as an electrical compensator [16,21]. Zimmermann et al also reported traps with activation energies of 0.66 and 0.73 eV in single-crystal substrates using the DLTS technique [22]. These energy levels were tentatively assigned for Fe substituting Ga at tetrahedral and octahedral positions, respectively.…”

“…These energy levels were tentatively assigned for Fe substituting Ga at tetrahedral and octahedral positions, respectively. Titanium (Ti) is another possible deep-level defect with activation energy of 0.95 eV, which originates due to octahedral Ga substitution [22]. Irmscher et al proposed that Co impurity may be responsible for trap levels at 0.55 and 1.04 eV [23].…”