GaN Remote Epitaxy on the III-Nitride Substrates by MOCVD and its Exfoliation

Abstract

3D heterogeneous integration technology has recently been introduced to manufacture semiconductors with complex and diverse functions. To implement this technology, the production of a freestanding membrane is essential. It is used by growing an epitaxial film using van der Waals epitaxy and remote epitaxy and then peeling it off. However, some difficulties exist when implementing these methods using only metal-organic chemical vapor deposition (MOCVD) equipment. In particular, in the case of gallium nitride (GaN), it is grown using gases such as hydrogen and ammonia at a high temperature of over 1000 degrees, and since substrate decomposition and synthesis proceed simultaneously, GaN van der Waals epitaxy and remote epitaxy using only MOCVD are almost impossible. This dissertation reports the results of research on GaN remote epitaxy using only MOCVD equipment. Through basic experiments, I have presented a successful strategy for III-Nitride remote epitaxy in MOCVD, and GaN remote hetero-epitaxy on the AlN template and GaN remote homo-epitaxy on the GaN template were studied. Through pre-experiments, I have identified the stability problem of two-dimensional (2D) materials due to substrate damage under high-temperature MOCVD growth conditions and found that factors such as temperature, gas, type of substrate, and peelability must be considered in order to implement the complete III-Nitride remote epitaxy. Based on these strategies, GaN remote hetero-epitaxy was attempted by transferring graphene onto the AlN template. GaN remote hetero-epitaxy that could be exfoliation under low-temperature growth conditions was successful. However, I discovered a problem of non-exfoliation after high-temperature growth, and it was confirmed that the problem was caused by damage to graphene due to nano-sized pits (structural problem) on the surface of the AlN template. Next, I studied GaN remote homo-epitaxy with the question, 'Is GaN remote homo-epitaxy using only MOCVD really impossible because it cannot avoid 2D material damage caused by the substrate decomposition?'. To avoid 2D materials damage due to exposure to high-temperature and active gas as much as possible, the surface of 2D materials was covered with low-temperature GaN growth, and even after high-temperature growth, the 2D materials were intact and peelable. As a result, In the case of graphene, it was confirmed that the remote epitaxial phenomenon appeared, and in the case of h-BN, the van der Waal epitaxial phenomenon appeared. These results show that GaN remote epitaxy is possible using only MOCVD, and that it can be used only with MOCVD equipment currently used in the industry. Therefore, if further research continues based on the results of this study in the future, it is expected that it will greatly contribute to the emerging next-generation semiconductor industry.