Non-logic Devices in Logic Processes by Yanjun Ma & Edwin Kan

Author:Yanjun Ma & Edwin Kan
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

The minority injection transport in p–n diodes and the thermionic emission in Schottky diodes actually happen in both diodes, just which mechanism is more dominant depending on the barrier height. For p–n diodes where the barrier height is larger than 0.8 eV, minority injection is much larger than thermionic emission, and hence the transport is bipolar. To establish or eliminate the minority carriers at the turn-on stage, the transport is slow. For Schottky diodes with less than 0.6 eV barrier, minority injection can be ignored.

Comparing with the p–n diodes, Schottky diode has low turn-on voltage, fast recovery time, and low junction capacitance. As a result Schottky diodes are popular for RF applications, e.g., at frequency of up to the terahertz domain and RF power detection circuits (Rivera, 2001). For example, Schottky diodes have been used in RF detectors and mixers at frequencies up to 50 GHz. Terahertz detectors are designed and fabricated using 0.13 μm CMOS process (Han et al., 2011). To achieve the cutoff high frequency, the designers used polysilicon gate-separated Schottky diodes with a 16 unit-cell structure, each with area of 0.4 × 0.4 μm2, with a total series resistance of 8 Ω and junction capacitance of 10 fF, yielding a cutoff frequency of 2 THz. The Schottky diode is integrated with on-chip patch antenna and preamplifier to achieve 280 GHz detector operation that performs better than other competing technologies.

Schottky diodes are also used as rectifiers in switched-mode power supplies. The low forward voltage and fast recovery time lead to increased efficiency which is especially important for RFID application (Jamali et al., 2004).

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