Submillimeter-Wave Quasi-Vertical GaAs Schottky Diodes Integrated on Silicon Membranes

Abstract

GaAs Schottky diodes are the central component of Terahertz (THz) metrology instrumentation. The frequency translating property of the Schottky diode is used in ground and space based observatories and for characterization of other THz devices. As detectors, GaAs Schottky diodes are used for measuring signal power levels, as mixers they are used in heterodyne receivers, and as variable capacitors they are used in frequency multipliers.The focus of this dissertation is the integration of GaAs Schottky diodes on silicon-on-insulator (SOI) substrate carriers to better control the device parasitics and to accommodate assembly of fully integrated diode-based circuits. During research into this process, a unique quasi-vertical diode geometry was developed in which the ohmic contact lies directly below the Schottky anode. While similar in concept to the first whisker contacted Schottky diodes, the quasi-vertical diode is nevertheless a planar device that is readily integrated with other components supported by the SOI substrate, including beamleads for electrical connection. To illustrate the advantages of this technology, 40-to-80 GHz doublers and a new 40-to-160 GHz quadrupler were designed and implemented using the quasi-vertical diodes and heterogeneous integration methods developed in this research. These multipliers are the first demonstrated fully-integrated GaAs varactor circuits fabricated on SOI, yielding record performance in multiplication efficiency, and demonstrating the benefits of the novel diode architecture and substrate replacement technology.ii

Steady-state thermal analysis of an integrated 160 GHz balanced quadrupler based on quasi-vertical Schottky diodes

“…The chip analyzed in this work is based on the 160 GHz balanced quadrupler detailed in [3]. The finite element method solution to the heat equation is aquired using Ansys R Mechanical, using the thermal conductivities measured above.…”

“…Furthermore, all the non-contact surfaces of the block are assumed to be at room temperature, i.e. 23.0 • C. The quadrupler chip is designed [3] such that it is suspended in the waveguide block, with protruding gold beam leads clamping it to the waveguide block at the input and output (see Figure 3(a)). Two additional beamleads protrude from hairpin bias chokes and are bonded to a quartz-supported filter that sits in the block.…”

“…The quasi-vertical Schottky diode geometry, thoroughly discussed in [2] [3], consists of a thin GaAs mesa (1.28 µm) that has been wafer-bonded to a host silicon-on-insulator (SOI) substrate ( Fig.1). The ohmic contact is formed prior to the epitaxial transfer, and the GaAs is not relied upon for structural integrity.…”

Micromachined On-Water Probes for Characterization of Terahertz Devices and Circuits

“…Due to its relatively low conductivity, however, the 1.0 µm thick nickel layer is deposited only over a small area near contact points, as illustrated in Fig. 2.19a [25].…”

Electronic Network Analyzer Calibration for Submillimeter Wafer Measurements

“…Simulated results, for a low frequency proof of concept, of the diode model presented in [10] can be seen in figure 12. Figure 12 shows the significant variability of impedances of the diode at three different bias points.…”