Xurui Mao

Optoelectronic Mixer Based on Graphene FET

We present optoelectronic mixing phenomenon in graphene FET (GFET) and give a brief analysis for the first time. Demonstrated by a measurement system, two operating modes of optoelectronic mixer (OE-mixer) circuits are proposed, either of them mixing optical and electrical signals directly using a single GFET. Optoelectronic conversion losses of 24 and 35 dB are obtained in a 50-Ω impedance system, respectively. GFET OE-mixer might be of strong importance for radio over fiber systems, millimeter wave, and terahertz frequencies applications.

Monolithic Integration of Si 3 N 4 Microring Filters With Bulk CMOS IC Through Post-Backend Process

An experimental demonstration of backend monolithic integration of Si3N4 microring filter with bulk complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC) is accomplished using CMOS postbackend process. Si3N4 photonic layer is integrated on the top surface of CMOS IC die which is manufactured in commercial CMOS foundry. The Si3N4 microring filters in photonic layer are fabricated using CMOS postbackend process with only two additional lithography steps. The filters can be thermally tuned by microheaters integrated in CMOS circuits, which are controlled by transmission gates. A measured optical transmission spectrum and a dynamic characteristic of the integrated filter are provided.

A Pure Frequency Tripler Based on CVD Graphene

In this letter, the chemical vapor deposition grown single-layer graphene with micrometer scale graphene flakes interspersed on the surface has been first used to implement field-effect transistors (FETs) for the purpose of frequency tripling. Two Dirac points can be observed in the transfer curves of the designed FETs, which are essential to generate pure third harmonic with ambipolar graphene. With an input of 1 kHz, more than 94% of the output signal RF power is concentrated at 3 kHz. To the best of our knowledge, it is the highest output spectral purity for reported frequency triplers. The excellent spectral purity, combined with the superhigh carrier mobility of graphene, makes this graphene-based frequency tripler a very promising candidate for the ultrahigh-frequency electronic applications.

Graphene Field-Effect Transistor Current Source With Double Top-Gates and Double Feedback

This letter proposes a graphene field-effect transistor (GFET) device with double top-gates and double feedback. An intuitive explanation of the device is provided and its performance is verified by numerical solution of the GFET large signal model in the p- and n-type regions. Simulation shows that the device can provide full current saturation within a large voltage range using a typical GFETs structure. The saturation current can be adjusted using a control voltage and other circuit parameters, which makes it a voltage-controlled current source suitable for analog and flexible circuit applications.

Monolithic optoelectronic integrated broadband optical receiver with graphene photodetectors

Abstract Optical receivers with potentially high operation bandwidth and low cost have received considerable interest due to rapidly growing data traffic and potential Tb/s optical interconnect requirements. Experimental realization of 65 GHz optical signal detection and 262 GHz intrinsic operation speed reveals the significance role of graphene photodetectors (PDs) in optical interconnect domains. In this work, a novel complementary metal oxide semiconductor post-backend process has been developed for integrating graphene PDs onto silicon integrated circuit chips. A prototype monolithic optoelectronic integrated optical receiver has been successfully demonstrated for the first time. Moreover, this is a firstly reported broadband optical receiver benefiting from natural broadband light absorption features of graphene material. This work is a perfect exhibition of the concept of monolithic optoelectronic integration and will pave way to monolithically integrated graphene optoelectronic devices with silicon ICs for three-dimensional optoelectronic integrated circuit chips.

Theoretical study of terahertz active transmission line oscillator based on RTD-gated HEMT

In this paper, a new kind of terahertz oscillator is presented using plasma wave excitation in a resonant tunnel diode (RTD) gated high electron mobility transistor (HEMT). The plasma wave arising from the RTD-gated HEMT is equivalent to active transmission lines and induces negative differential conductance (NDC) of the oscillator. The proposed RTD-gated HEMT oscillator is more compact and has higher oscillation frequency than the transmission line loaded traditional RTD oscillator duo to plasma wave effect. This paper analyses and calculates the oscillation conditions, the relationships between device structures, oscillation frequency and the output power of the oscillator. The presented work may provide a new concept for fabricating terahertz oscillator.

A graphene based frequency quadrupler

Benefit from exceptional electrical transport properties, graphene receives worldwide attentions, especially in the domain of high frequency electronics. Due to absence of effective bandgap causing off-state the device, graphene material is extraordinarily suitable for analog circuits rather than digital applications. With this unique ambipolar behavior, graphene can be exploited and utilized to achieve high performance for frequency multipliers. Here, dual-gated graphene field-effect transistors have been firstly used to achieve frequency quadrupling. Two Dirac points in the transfer curves of the designed GFETs can be observed by tuning top-gate voltages, which is essential to generate the fourth harmonic. By applying 200 kHz sinusoid input, arround 50% of the output signal radio frequency power is concentrated at the desired frequency of 800 kHz. Additionally, in suitable operation areas, our devices can work as high performance frequency doublers and frequency triplers. Considered both simple device structure and potential superhigh carrier mobility of graphene material, graphene-based frequency quadruplers may have lots of superiorities in regards to ultrahigh frequency electronic applications in near future. Moreover, versatility of carbon material system is far-reaching for realization of complementary metal-oxide-semiconductor compatible electrically active devices.

Tunable photoresponse in graphene photodetector with novel split local back-gates based on heavily doped silicon

We have demonstrated a graphene photodetector with tunable photoresponse via electrostatic doping with split local back-gates formed by heavily doped silicon for the first time. A tunable photocurrent from 0 nA to 250 nA is obtained.

An adaptive impedance tracking frontend for inductively powered body sensor nodes

In this paper, an adaptive impedance tracking front end for inductively powered body sensor node is presented. By implementing a novel impedance matching network with digitally tunable capacitor array in an inductively powered energy hsarvester chip, the system can adaptively maintain impedance match with the coil under influences from nearby human body or metal object, deformation and in homogeneity from manufacture. The experiment demonstrates that the system can effectively maintain resonant frequency of the receiver antenna, boost resonance amplitude of coil and rectifier output significantly compared with fixed matching networks in on-body application.

Characterization of Graphene TFET for Subterahertz Oscillator

This paper presents the frequency and output power characteristics of oscillators in the graphene tunneling FETs (GTFET) technology. In order to acquire these characteristics, the practical operating conditions of GTFET oscillators are carefully analyzed, and then, the device parameters are simplified to an equivalent circuit and the I/V large signal model is approximated by a compact form. Expressions for the maximum oscillation frequency, maximum output power, and the relationship between frequency and power are given combing the equivalent circuit and the simplified model. In addition, the key device parameters that can be used to improve the performance of a GTFET oscillator are also discussed.