TeraFET terahertz detectors with spatially non-uniform gate capacitances

A non-uniform capacitance profile in the channel of a THz field-effect transistor (TeraFET) could significantly improve the THz detection performance. The analytical solutions and simulations of the hydrodynamic equations for the exponentially varying capacitance versus distance showed ~10% increase in the responsivity for the 130 nm Si TeraFETs in good agreement with numerical simulations. Using the numerical solutions of the hydrodynamic equations, we compared three different Cg configurations (exponential, linear and sawtooth). The simulations showed that the sawtooth configuration provides the largest response tunability. We also compared the effects of the non-uniform capacitance profiles for Si, III-V, and p-diamond TeraFETs. The results confirmed a great potential of p-diamond for THz applications. Varying the threshold voltage across the channel could have an effect similar to that of varying the gate-to-channel capacitance. The physics behind the demonstrated improvement in THz detection performance is related to breaking the channel symmetry by device geometry of composition asymmetry. The generation and detection of terahertz (THz) radiation has been a very active area over the recent decades. Occupying the frequency range of 100 GHz-30 THz, THz radiation fills the frequency gap between the electronics and photonics. Initially, THz science and technology were explored in the fi eld of astronomy, and expanded rapidly since 1990s following the development of THz spectroscopy. By now, the real-life applications of THz-based technology can be found in various fields, including the biomedical engineering, VLSI testing, wireless communication, and object sensing. A high-quality THz signal detector plays a crucial role in almost all THz applications. The present-day THz sensors are mostly semiconductorbased, with Schottky devices being the dominant product. Recently, plasma-wave field-effect transistor (FET) detectors have attracted more attention as they offer high responsivity, ultra-fast response time, and are highly tunable by gate, doping, and channel structures. Moreover, plasma-wave THz FETs (TeraFETs) are particularly promising for next-generation communication applications, since these devices exhibited exceptional detection performance in the 200-400 GHz band allocated for beyond-5G communication. Despite all those merits, plasmonic TeraFETs still face a variety of challenges, including the fabrication burden, requirement for high sensitivity, and noise issues. Among others, the detection sensitivity/responsivity is always a key issue. Due to the existence of scattering, the response voltage of TeraFETs can be limited, which impairs the device performance. As was discussed in [25], further improvement in the TeraFET responsivity is required to enable their application in 6G communication. In this paper, we show that the implementation of a spatially non-uniform gate capacitance (Cg) profile could significantly enhance the responsivity. A non-uniform Cg profile can be realized by altering the barrier layer width. For example, consider a Si FET with a composite barrier layer of SiO2 and HfO2. We may profile the HfO2 layer by adjusting the etch rate to achieve a non-uniform Cg(x) (see Section A of Supplementary Material).

[1]  Controlling the number of discharge current pulses in an atmospheric dielectric barrier discharge by voltage waveform tailoring , 2021 .

[2]  M. Shur,et al.  Collision dominated, ballistic, and viscous regimes of terahertz plasmonic detection by graphene , 2020, 2012.11423.

[3]  I. Kim,et al.  A review of doping modulation in graphene , 2018, Synthetic Metals.

[4]  I. Akimoto,et al.  High carrier mobility in ultrapure diamond measured by time-resolved cyclotron resonance , 2014 .

[5]  Dyakonov-Shur instability across the ballistic-to-hydrodynamic crossover , 2018, 1801.01501.

[6]  S. Takagi,et al.  On the universality of inversion layer mobility in Si MOSFET's: Part I-effects of substrate impurity concentration , 1994 .

[7]  Michael S. Shur,et al.  Sub-terahertz testing of millimeter wave Monolithic and very large scale integrated circuits , 2019 .

[8]  Thomas W. Crowe,et al.  GaAs Schottky diodes for THz mixing applications , 1992, Proc. IEEE.

[9]  Michael S. Shur,et al.  Plasmonic detectors and sources for THz communication and sensing , 2018, Defense + Security.

[10]  Michael S. Shur,et al.  Electron mobility in modulation-doped AlGaN-GaN heterostructures , 1999 .

[11]  Cyril C. Renaud,et al.  The 2017 terahertz science and technology roadmap , 2017, Journal of Physics D: Applied Physics.

[12]  M. Shur,et al.  Plasmonic terahertz detector response at high intensities , 2012 .

[13]  M. Shur,et al.  Current-induced terahertz oscillations in plasmonic crystal , 2012 .

[14]  M. Shur,et al.  p-Diamond as candidate for plasmonic terahertz and far infrared applications , 2018, Applied Physics Letters.

[15]  S. Rudin,et al.  Effects of oblique wave propagation on the nonlinear plasma resonance in the two-dimensional channel of the Dyakonov-Shur detector , 2011, 2011 International Semiconductor Device Research Symposium (ISDRS).

[16]  M. Shur,et al.  Graphene based plasma-wave devices for terahertz applications , 2020 .

[17]  M. Shur,et al.  Nonresonant Detection of Terahertz Radiation in Field Effect Transistors , 2002 .

[18]  H. Terças,et al.  Terahertz Laser Combs in Graphene Field-Effect Transistors , 2019, ACS Photonics.

[19]  Masayoshi Tonouchi,et al.  Cutting-edge terahertz technology , 2007 .

[20]  D’yakonov-Shur instability in a ballistic field-effect transistor with a spatially nonuniform channel , 1999 .

[21]  M. Shur,et al.  Acoustic phonon scattering of two-dimensional electrons in GaN/AlGaN heterostructures , 2002 .

[22]  M. I. Dyakonov.  Generation and detection of Terahertz radiation by field effect transistors , 2010 .

[23]  Michael S. Shur,et al.  Introduction to electronic devices , 1995 .

[24]  Holger Blaschke,et al.  Investigations on SiO2/HfO2 mixtures for nanosecond and femtosecond pulses , 2010, Laser Damage.

[25]  Takashi Taniguchi,et al.  Resonant terahertz detection using graphene plasmons , 2018, Nature Communications.

[26]  M. Shur,et al.  Unified charge control model and subthreshold current in heterostructure field-effect transistors , 1990, IEEE Electron Device Letters.

[27]  Michael S. Shur,et al.  Theory and measurement of plasmonic terahertz detector response to large signals , 2014 .

[28]  A. Toriumi,et al.  Experimental study of threshold voltage fluctuation due to statistical variation of channel dopant number in MOSFET's , 1994 .

[29]  M Unlu,et al.  Significant performance enhancement in photoconductive terahertz optoelectronics by incorporating plasmonic contact electrodes. , 2013, Nature communications.

[30]  R. Lewis.  A review of terahertz detectors , 2019, Journal of Physics D: Applied Physics.

[31]  Mikhail I. Dyakonov,et al.  Field Effect Transistors for Terahertz Detection: Physics and First Imaging Applications , 2009, 0907.2523.

[32]  Simon Deleonibus,et al.  Investigation of SiO2/HfO2 gate stacks for application to non-volatile memory devices , 2005 .

[33]  M. Shur,et al.  Detection, mixing, and frequency multiplication of terahertz radiation by two-dimensional electronic fluid , 1996 .

[34]  Michael S. Shur,et al.  Plasma wave electronics: novel terahertz devices using two dimensional electron fluid , 1996 .