Silicon Integrated HBV Frequency Multipliers

We present the technology and RF characterisation results for silicon integrated heterostructure barrier varactor (HBV) based frequency multipliers. Two types of devices are shown: a frequency tripler for W-band frequency range [1], and a frequency quintupler operating between 440 GHz and 490 GHz [2]. The In0.53Ga0.47As/ In0.52Al0.48As/ AlAs material structure was transferred on silicon host substrate in a process of low-temperature plasma-assisted wafer bonding. The transferred material is utilised to fabricate HBV diodes, while the silicon serves as a substrate for microstrip circuity. The technology of silicon integrated W-band frequency tripler is based on the InP technology presented in [3]. After processing HBV diodes and gold electroplating microstrip component, the individual devices are separated by dicing, and then the silicon substrate is mechanically thinned down to 80 μm. However, the lapping process does not assure accurate final substrate thickness. Therefore, use of silicon-on-insulator (SOI) with a buried oxide layer which acts as an etch.-stop layer is an interesting solution. The in-house developed SOI technology was used to fabricate frequency quintupler. The circuits are defined from a 20 μm thick and high resistivity device layer of the SOI wafer. The silicon handle is thinned by reactive ion etching. Then, the individual circuits are defined and separated by back-side photolithography and a Bosch process. Although only 20 μm thick, the quintupler circuits are mechanically robust, easy to handle and assemble. Prior to the RF characterisation the frequency multipliers are assembled in waveguide split-blocks. The devices are driven with an input power from commercial power amplifiers. The measured output power (and the 3-dB bandwidth) of these devices is 184 mW (9%) and .2.8 mW (4%) for the frequency tripler and quintupler respectively. The developed epitaxial transfer and SOI technology can be used for Schottky diode based frequency multipliers and mixer.[1] A. Malko, et al., "Silicon integrated InGaAs/InAlAs/AlAs HBV frequency tripler," IEEE Electron Device Letters, vol. 34, pp. 843 - 845 2013.[2] A. Malko, et al., "A 474 GHz HBV frequency quintupler integrated on a 20-μm thick silicon substrate," submitted to IEEE Transactions on Terahertz Science and Technology, 2014.[3] J. Vukusic, et al., "Monolithic HBV-based 282 GHz tripler with 31 mW output power," IEEE Electron Device Letters, vol. 33, pp. 800 - 802, 2012