Linli Xie

Terahertz Diode Arrays and Differential Probes based on Heterogeneous Integration and Silicon Micromachining

Due to the technological needs of the radio astronomy and remote sensing scientific communities, as well as emerging applications in the areas of imaging, security, and broadband communications, terahertz and submillimeter-wave electronics continues to be an area of growth and increasing interest for academic researchers, government laboratories, and industry. The recent establishment of a commercial infrastructure for test and measurement instrumentation in this spectral region has fueled this growth and the emergence of CMOS as a submillimeter-wave technology has greatly expanded access to this spectral region by providing circuit designers with a platform for realizing terahertz circuits without need for specialized fabrication facilities or processes. The continued emergence of new terahertz devices has created a need for improved approaches to packaging, integration, and measurement tools for diagnostics and characterization in this portion of the spectrum. This paper focuses on progress in two paral...

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

This work reports on a steady-state thermal analysis of a 160 GHz balanced quadrupler, based on a quasi-vertical varactor Schottky diode process, for high power applications. The chip is analyzed by solving the heat equation via the 3D finite element method. Time-Domain Thermoreflectance (TDTR) was used to measure the thermal conductivity of the different materials used in the model. A maximum anode temperature of 64.9°C was found from the simulation. The addition of an extra beam lead connected to the block, for heat sinking, was found to reduce this maximum temperature to 41.0°C.

A micromachined differential probe for on-wafer measurements in the WM-1295 (140–220 GHz) band

This paper describes the first-reported development of a micromachined differential probe for direct on-wafer measurements operating in the WM-1295 (140–220 GHz) frequency band. Design and fabrication of the probe, which includes integrated circuitry for converting the input of a single-ended vector network analyzer to differential mode, are described and an on-wafer calibration procedure for extracting the probe mixed-mode scattering parameters. is detailed.

A monostatic coded aperture reflectometer for imaging at submillimeter-wavelengths

A prototype imaging reflectometer based on the coded aperture technique and operating in the WR-1.5 (500–750 GHz) frequency band is described. Masks for the coded aperture system are realized through optical modulation of the conductivity of a high-resistivity silicon wafer. A network model representation of the imaging system is developed and applied to measuring beam maps of a submillimeter-wave diagonal horn antenna.

An Epitaxy Transfer Process for Heterogeneous Integration of Submillimeter-Wave GaAs Schottky Diodes on Silicon Using SU-8

This letter describes a new approach for fabricating quasi-vertical submillimeter-wave GaAs Schottky diodes heterogeneously integrated to high-resistivity silicon substrates. The new method is robust and eliminates previous processing steps that were prone to result in wafer fracture and delamination. Diodes fabricated with the new process and measured in the 325–500 GHz range using on-wafer RF probes exhibits low parasitic capacitance and series resistance, achieving device characteristics comparable to the prior state-of-the-art submillimeter-wave diodes.

An Integrated 100-element schottky varactor diode array for sideband generation at 1.6 THz

This work describes the development and implementation of a Schottky varactor diode array for sideband generation at 1.6 THz. The array integrates 100 planar diodes into an array of bowtie antennas to act as a tunable phase-shifter for reflected submillimeter-wave radiation. Measurements performed to characterize the array indicate that 20° of phase shift is achieved as the diode bias voltage is swept between 0.3 and -4 Volts, yielding an estimated sideband conversion loss of 26 dB.