As one of the most important and influential advanced technologies of the twentieth century, the influence and significance of semiconductor technology has extended into the twenty-first century. As the foundation of information society, the semiconductor technology has been pushing the human society forward while changing the production, daily life, interpersonal communication, and even the way of thinking of mankind. Semiconductor materials have been playing a critical role in the development of the semiconductor technology. The first transistor invented in 1947 was based on the semiconductor of germanium (Ge) with a room temperature band gap of 0.66 eV. The first integrated circuit born in 1958 was actually of a mixed type, and the first true monolithic integrated circuit appeared in 1961 and employed germanium. Silicon (Si) with a room temperature band gap of 1.12 eV replaced germanium in 1965 to be the major material for semiconductor integrated circuits, and nowadays, remains the principal semiconductor material in microelectronics. The vast majority of the semiconductor industries, either the integrated circuit or the photovoltaic cell industry, are still based on silicon. Silicon and germanium are generally referred to as the first-generation semiconductors for their comparatively long history of development. The second-generation semiconductors including both gallium arsenide (GaAs, with a room temperature band gap of 1.42 eV) and indium phosphide (InP, with a room temperature band gap of 1.35 eV) were introduced in the 1970s and primarily adopted in ultrahigh-speed devices, microwave power devices, and integrated circuits. InP integrated circuits were not commercially available until 1997. Major progresses in the third-generation (wide band gap) semiconductors such as gallium nitride (GaN, with a room temperature band gap of 3.45 eV) and silicon carbide (SiC, with a room temperature band gap of 3.25 eV for 4H-SiC) have been made since the end of the twentieth century.