Properties and applications of SiGe nanodots

The use of SiGe strained layers for BiCMOS technology has been prevailing in the market place for high-speed and high-frequency mixed mode applications. The advantages of using SiGe are due to its compatibility with mainstream Si CMOS processing. SiGe has also been gradually making its way to the mainstream strained layer CMOS as well. In this paper, we will discuss SiGe quantum structures, which have the unique properties due to their nanosize effects and the presence of strain. We will describe the growth of SiGe quantum dots on Si. First, for dot growth, issues such as the growth conditions and their effects on the dot morphology will be reviewed. We will focus on the dependence of growth temperature on the size and also show the mechanisms of uniform dot formation. The basic issues such as vertical correlation and dot morphology evolution will be addressed in relation to the critical thickness of Ge quantum dot superlattices. Both interband and intersubband photoluminescence properties of Ge quantum dot superlattices will be discussed as functions of dot size, excitation power, growth temperature, superlattice period, and Ge concentration. We will also discuss quantum dot pin photodetectors for 1.3-1.55 μm for integration with Si technology for communications applications. Potential light emission from dots will be described and the characteristics of fabricated LED devices will be reported. Likewise, we will show the results of intersubband properties of boron-doped and modulation-doped Ge quantum dot superlattices in reference to intersubband absorption as studied by FTIR. We will describe the quantum dot pip photodetectors for 3-5 and 8-12 μm applications.