An active interferometric method for extreme impedance on-wafer device measurements

Nano-scale devices and high-power transistors present extreme impedances, which are far removed from the 50-Ω reference impedance of conventional test equipment, resulting in a reduction in the measurement sensitivity as compared with impedances close to the reference impedance. This letter describes a novel method based on active interferometry to increase the measurement sensitivity of a vector network analyzer for measuring such extreme impedances, using only a single coupler. The theory of the method is explained with supporting simulation. An interferometry-based method is demonstrated for the first time with on-wafer measurements, resulting in an improved measurement sensitivity for extreme impedance device characterization of up to 9%

Microwave Properties of 2D CMOS Compatible Co-Planar Waveguides Made from Phosphorus Dopant Monolayers in Silicon

Low-dimensional microwave interconnects have important applications for nanoscale electronics, from complementary metal–oxide-semiconductor (CMOS) to silicon quantum technologies. Graphene is naturally nanoscale and has already demonstrated attractive electronic properties, however its application to electronics is limited by available fabrication techniques and CMOS incompatibility. Here, the characteristics of transmission lines made from silicon doped with phosphorus are investigated using phosphine monolayer doping. S-parameter measurements are performed between 4–26 GHz from room temperature down to 4.5 K. At 20 GHz, the measured monolayer transmission line characteristics consist of an attenuation constant of 40 dB mm−1 and a characteristic impedance of 600 Ω. The results indicate that Si:P monolayers are a viable candidate for microwave transmission and that they have a.c. properties similar to graphene, with the additional benefit of extremely precise, reliable, stable, and inherently CMOS compatible fabrication

Solution-Processed InAs Nanowire Transistors as Microwave Switches

The feasibility of using self?assembled InAs nanowire bottom?gated field?effect transistors as radio?frequency and microwave switches by direct integration into a transmission line is demonstrated. This proof of concept is demonstrated as a coplanar waveguide (CPW) microwave transmission line, where the nanowires function as a tunable impedance in the CPW through gate biasing. The key to this switching capability is the high?performance, low impedance InAs nanowire transistor behavior with field?effect mobility of ?300 cm2 V?1 s?1, on/off ratio of 103, and resistance modulation from only 50 ? in the full accumulation mode, to ?50 k? when the nanowires are depleted of charge carriers. The gate biasing of the nanowires within the CPW results in a switching behavior, exhibited by a ?10 dB change in the transmission coefficient, S21, between the on/off switching states, over 5–33 GHz. This frequency range covers both the microwave and millimeter?wave bands dedicated to Internet of things and 5G applications. Demonstration of these switches creates opportunities for a new class of devices for microwave applications based on solution?processed semiconducting nanowires

High-frequency electromagnetic characterisation and modelling of extreme impedance devices.

Nanoscale devices have an intrinsic impedance significantly different than the 50-Ω reference impedance of the measurement systems. This results in a high reflection coefficient, limiting the accuracy of the measurements leading in imprecise characterisation. In addition, the small dimensions of nanoscale devices forbid their physical access using conventional microwave probes. It is therefore essential to investigate new measurement techniques and to develop access structures, for nanoscale high-frequency characterisation. This thesis presents the fabrication of new access structures and calibration standards based on a co-planar waveguide design, for the microwave measurement of nanoscale devices. The calibration structures are used for the first time to move the measurement reference plane to a nanoscale device using a calibration algorithm. Furthermore, to mitigate for the impedance mismatch between the devices and the measurement systems, a new measurement technique based on active interferometry was developed. The method is based on a simplified measurement configuration and a custom calibration that mitigates for the finite directivity of the couplers used for the implementation of the technique, achieving a significantly higher measurement sensitivity for extreme impedances compared to conventional techniques. To showcase the potential usage of nanoscale devices within a microwave application, a prototype coplanar-waveguide switch has been developed that incorporates indium arsenide nanowires. The prototype device has shown encouraging high-frequency switching capabilities and an equivalent circuit model was developed that matches the high-frequency S-parameters of the device within an 8% error. Lastly, the electromagnetic coupling between calibration standards within an on-wafer environment has been successfully measured and investigated using an electro-optic on-wafer measurement system. The coupling can affect the accuracy of a calibration performed, and can have critical ramifications to the accurate characterisation of nanoscale devices

Dynamic Temperature Measurements of a GaN DC/DC Boost Converter at MHz Frequencies

For reliability predictions, gallium nitride transistors require accurate estimations of the peak operating temperatures within the device. This paper presents a new application of thermoreflectance-based temperature measurements performed on a gallium nitride high electron mobility transistor. The submicron spatial and nanosecond temporal resolutions of the measurement system enables for the first time, the dynamic temperature measurement of a transistor operating up to 5 MHz. The GaN transistor is first biased in class-A and excited with a 1 MHz AC signal to demonstrate the dynamic temperature measurement. The transistor is then incorporated in a 20–40 V DC/DC boost converter to measure the dynamic temperature distributions across the semiconductor die operating under real loading conditions at 1 and 5 MHz switching frequencies. This technique captures the temperature variations that occur during the switching of the transistor and the recorded peak temperatures are 7.