Study Of Si-based Ge Nanoheteroepitaxy With Porous Alumina Membrane

In recent years, relentless pursue of Moore’s law leads to the device feature size approaching bottleneck of electronic devices, especially the interconnect bandwidth density. Silicon photonics has begun to realize commercialization. IBM believe the next decade is important for the lab to fab of silicon photonics. They demonstrated the feasibility of silicon photonics for chip manufacturing. The high speed of light can solve bandwidth limitations of servers, datacenters and supercomputers. Intel has introduced Light Peak in2009, allied with Apple, they released the new interface on Mac computers, Thunderbolt. The optical version of Thunderbolt can increase data rate to100Gbps, which is much larger than0.48Gbps of USB2.0. For the first time, Thunderbolt make a great advancement in interconnections between chips. Though the feasibility has been proved, the cost of silicon photonics should be decreased for civil use. The field of silicon photonics is now advancing at a rapid pace and there is still a lot of research to be done.This thesis mainly discuss properties of Ge/Si system, which can be used as devices for sili-con photonics. Si-based Ge quantum dots can be used as light source, or even quantum computing. Si-based Ge films can be used as photodetectors, which has been already used in commercial. It is well known that the Stranski-Krastinov(S-K) growth mode is followed during molecular beam epitaxy of Ge on Si due to strain caused by the4.2%lattice mismatch between them. However S-K mode is random and uncontrollable, one cannot rely on it for outstanding devices fabrication. Nanoheteroepitaxy, which uses nano-patterns as templates for heteroepitaxy, has attracted a lot of attentions. For example, Ge quantum dots achieved by S-K growth mode have no quantum confine-ment effect due to the large size of dots normal to growth direction. However, nanoheteroepitaxy can confine the lateral dimension of dots with nano-patterns, and quantum confinement effect can be improved. This thesis adopted porous anodic alumina as mask to transfer nano-patterns on Si substrate without any lithography, which can be the basis of Ge/Si heteroepitaxy.The first chapter introduces the background of silicon photonics, the properties of Ge and the research progress of Ge/Si devices. Chapter2describes the theoretical analyze of low-dimensional quantum systems. The effect of different properties of quantum dots on energy band structure was also simulated by nextnano software. Chapter3introduces the advantage of porous alumina mem-brane as mask for pattern transferring, the following experimental procedure and measurements. Chapter4shows fabrication and results of Ge quantum dots achieved by nanoheteroepitaxy. A density-temperature (D-T) relation was raised, which can be used to predict the optimal temper-ature for a certain pattern density. Chapter5describes selective epitaxial growth of Ge films on SiO2windows, TEM results show very high quality of Ge films. The shadow-etching technique decrease the window size to20nm, which can be used to grow defect-free Ge films. Chapter6conclude the previous work and suggest several possible ways in future work.