As a promising alternative to the Von Neumann architecture, in-memory computing holds the promise of delivering high computing capacity while consuming low power. Content addressable memory (CAM) can implement pattern matching and distance measurement in memory with massive parallelism, making them highly desirable for data-intensive applications. In this paper, we propose and demonstrate a novel 1-transistor-per-bit CAM based on the ferroelectric reconfigurable transistor. By exploiting the switchable polarity of the ferroelectric reconfigurable transistor, XOR/XNOR-like matching operation in CAM can be realized in a single transistor. By eliminating the need for the complementary circuit, these non-volatile CAMs based on reconfigurable transistors can offer a significant improvement in area and energy efficiency compared to conventional CAMs. NAND- and NOR-arrays of CAMs are also demonstrated, which enable multi-bit matching in a single reading operation. In addition, the NOR array of CAM cells effectively measures the Hamming distance between the input query and stored entries. Furthermore, utilizing the switchable polarity of these ferroelectric Schottky barrier transistors, we demonstrate reconfigurable logic gates with NAND/NOR dual functions, whose input-output mapping can be transformed in real-time without changing the layout. These reconfigurable circuits will serve as important building blocks for high-density data-stream processors and reconfigurable Application-Specific Integrated Circuits (r-ASICs). The CAMs and transformable logic gates based on ferroelectric reconfigurable transistors will have broad applications in data-intensive applications from image processing to machine learning and artificial intelligence.

Content-addressable memory (CAM) compares input search data with stored data, returning the address upon a match. CAMs offer high-speed parallel search, making them ideal for associative memory applications. CAMs are categorized into binary (BCAMs) and ternary CAMs (TCAMs). BCAMs store two states and require an exact match for a successful search, while TCAMs can store a third state, “don’t care” or “X”, always resulting in a match. Traditionally, CAMs are implemented using CMOS static random-access memory (SRAM). However, SRAM-based CAMs use ≥ 9 transistors, increasing the area and power dissipation. Recently, 2D reconfigurable transistors (RFETs) have emerged as a promising technology for TCAMs. 2D-RFET TCAMs offer high on/off ratio, low power consumption, non-volatile data storage, and low area requirement, using only 1T for realizing a CAM [1] .

Terahertz plasma oscillations in GaN HEMTs are simulated in a TCAD environment using the Fermi kinetics transport model. Parallels are drawn between the Boltzmann transport equation and the shallow water dynamics used in previous studies to explain the oscillations. The necessary simulation conditions needed to observe the oscillations in a TCAD environment are described. Further discussion on the significance of the average momentum relaxation time and the rationale for choosing its value are presented. Transient simulations of THz oscillations are demonstrated when the gate voltage is perturbed at the quiescent point. A physical theory of plasma oscillations is proposed by analyzing the oscillations of the channel electron concentration, electron temperature and electric field. The electron temperature and electric field profiles are observed to be out of phase with each other, alluding to the fact that the energy is exchanged back and forth between the hot electrons and the EM fields, leading to the excitation of plasma oscillations.

In this work, we describe the charge transport in two-dimensional (2D) Schottky barrier field-effect transistors (SB-FETs) based on the carrier injection at the Schottky contacts. We first develop a numerical model for thermionic and field-emission processes of carrier injection that occur at a Schottky contact. The numerical model is then simplified to yield an analytic equation for current versus voltage (I-V) in the SB-FET. The lateral electric field at the junction, controlling the carrier injection, is obtained by accurately modeling the electrostatics and the tunneling barrier width. Unlike previous SB-FET models that are valid for near-equilibrium conditions, this model is applicable for a broad bias range as it incorporates the pertinent physics of thermionic, thermionic field-emission, and field-emission processes from a 3D metal into a 2D semiconductor. The I-V model is validated against the measurement data of 2-, 3-, and 4-layer ambipolar MoTe_2 SB-FETs fabricated in our lab, as well as the published data of unipolar 2D SB-FETs using MoS_2. Finally, the model's physics is tested rigorously by comparing model-generated data against TCAD simulation data.

This work compares the current-voltage characteristics and convergence of two technology computer aided design (TCAD) solvers, a commercial hydrodynamic transport (CHT) solver, Sentaurus by Synopsys (Version R-2020.09), and the Fermi kinetics transport (FKT) solver developed at the Air Force Research Laboratory. These solvers are used to simulate and determine the convergence properties of the large-signal response of a conventional gallium nitride (GaN) high-electron mobility transistor (HEMT) at 1 GHz using drift-diffusion transport with constant electron mobility. We show that the large signal response of the HEMT is virtually the same in CHT and FKT with minor differences in their rate of convergence. This contrasts previous work in static simulations [1] where FKT had better convergence, showing that transient simulations are more computationally robust than static ones.

Various simulations of a GaN HEMT are used to study the behaviors of two different energy-transport models: the Fermi kinetics transport model and a hydrodynamics transport model as it is implemented in the device simulator Sentaurus from Synopsys. The electron transport and heat flow equations of the respective solvers are described in detail. The differences in the description of electron flux and the discretization methods are highlighted. Next, the transport models are applied to the same simulated device structure using identical meshes, boundary conditions, and material parameters. Static simulations show the numerical convergence of Fermi kinetics to be consistently quadratic or faster, whereas the hydrodynamic model is often sub-quadratic. Further comparisons of large signal transient simulations reveal the hydrodynamic model produces certain anomalous electron ensemble behaviors within the transistor structure. The fundamentally different electron dynamics produced by the two models suggest an underlying cause for their different numerical convergence characteristics.

As a result of the continually growing demand for wireless signals, the electromagnetic spectrum has become heavily crowded. An expedient route toward overcoming the spectrum scarcity is to create the key components of wireless transceivers, such as power amplifiers (PAs), using new semiconductor technologies that can operate at near-terahertz frequencies, while also delivering high output power on the order of 10's of W/mm. Owing to their large bandgap, ability to host polarization-induced two-dimensional electron gas (2DEG), superior electron transport properties at high temperatures, the ultrawide bandgap (UWBG) Al-rich AlGaN semiconductors [1] have become an attractive candidate for efficient power amplification at high frequencies [ Fig. 1(a) ].