## 1 Introduction  
Millimeter-wave Integrated circuits (MMW ICs) are designed to deal with the frequency bands from 30 GHz to 300 GHz that correspond to a wave-length of 10 mm to 1 mm. Recently, applications for all aspects of modern life have been proposed, such as: home entertainment media, consumer electronics, astronomy observations, aerospace communications and cutting-edge research. This draws attention to MMW ICs. The earliest MMW ICs were demonstrated in 1978 [1] and 1981 [2]. Twodecades later, MMW ICs were utilized for the military purpose. Furthermore, in the 1990s, mobile and wireless communications were developed prosperously; many MMICs [3; 4; 5; 6; 7; 8; 9; 10; 11; 12] were not only reported for military applications but also for civil applications. Most analog functions of a typical MMW communication system can be performed by monolithic integrated circuits like low noise amplifier (LNA), mixer, voltage-control oscillator (VCO), phase shifter, switch, power amplifier (PA) and so on. In addition, for some applications, which require medium power levels and large quantities of chips, MMW ICs are competitive, especially in large-scale production. Thus, III-V based MMICs such as GaAs and InP were popular at that time due to their superior performances. GaAs-based technologies have higher electron mobility than Si-based technologies and hence transistors can operate above 250 GHz. Also, GaAs transistors have wider bandgap, which leads to a relative insensitivity with respect to heat compared with Si transistors [13]. Most specifically, GaAs devices have relative lower noise than Si devices at high frequencies due to lower parasitics. However, the output power and noise performances of the GaAs-based transistors are still not good enough for some applications. This has resulted in the development of other high electron mobility transistors based on InP and GaN material systems. InP-based technologies have superior electron mobility than the more common semiconductors silicon and GaAs so that they can be utilized in high output power and high frequency MMICs [14]. InP-based technologies are popular in implementing optoelectronic devices such as laser diodes owing to their direct bandgap. Moreover, InP-based technologies are exploited for epitaxial indium gallium arsenide based optoelectronic devices. GaN-based technologies are developed for the applications of high voltage operation and high efficiency. With a reduction of the gate length, GaN-based devices can operate at higher frequencies in excess of W-band [15]. In automotive and electric car applications, GaN-based devices are more popular than other devices. Furthermore, nanotubes of GaN are introduced to realizing circuits for nanoscale electronics, optoelectronics and biochemical-sensing applications [16]. After the year 2000, silicon-based technologies gradually took over GaAs-based technologies in popularity for some III-V niche applications. Advances in silicon-based technologies have been aggressive and rapid. According to [PERSON]'s law [17], the period for a doubling in chip performance, that is, a combination of the effect of more transistors and their higher speed or operation frequency is 18 months. Thus, silicon-based technologies are promising and their performances can predictably catch up with those GaAs-based technologies in a short time. Also, silicon-based technologies have much better integration capability [13] than those in GaAs-based technologies. It is easier to integrate the baseband digital circuits into a single chip with MMW circuits in silicon-based technologies rather than that in GaAs-based technologies. Otherwise, an excessively large chip size is required. Note that the III-V based technologies still play an important role due to their superior performances in the field of mmw or sub-mmw circuits [18; 19; 20; 21]. Even Si-based technologies could be successively improved in the future.