RF systems based on silicon-on-sapphire technology

The major issues, which confronted the formation of very thin layers of silicon (30-100 nm) on sapphire substrates for application to mm-wave communication and sensors were investigated. The focus of the investigation was, and still is, to achieve a structure in which the modern CMOS technology, the mainstay technology and workhorse of the electronic revolution, can be affordably continued. In this context the application of device-quality thin film silicon-on-sapphire (TFSOS), obtained by Solid Phase Epitaxy (SPE), and the growth of strained silicon-germanium (SiGe) layers on these improved thin silicon films on sapphire have demonstrated enhanced devices and circuits performance. We have fabricated 250 nm and 100nm T-gated devices with noise figures as low as 0.9 dB at 2 GHz with an associated gain of 21 dB, and 2.5dB at 20 GHz, with an associated gain of 7.5dB, respectively. These performances resulted in distributed wide-band amplifiers (10 GHz BW, world record) and tuned amplifiers (15 dB peak gain, 4 GHz BW), among others. Additionally, VCOs (25.9 GHz) and frequency dividers in excess of 30 GHz were fabricated with devices with f_t (f_max) of 105 GHz (50 GHz) for n-channel and 49 GHz (>110 GHz) for p-MODFETs with 100 nm T-gates (strained Si_0.2Ge_0.8 on a relaxed Si_0.7Ge_0.3 heterostructure).