Nine-state resonant tunneling diode memory

The authors demonstrate an epitaxial series combination of eight pseudomorphic AlAs/In_0.53Ga_0.47As/InAs resonant tunneling diodes (RTDs) grown by molecular beam epitaxy on InP. This series RTD produces an eight-peak multiple negative differential resistance characteristic with a peak-to-valley current ratio (PVR) exceeding 2 per peak at a peak current density of approximately 6 kA/cm ². Hysteresis in the current-voltage characteristic is reduced by uniformly Si doping the double-barrier resonant tunneling region at a density of 5×10¹⁶ cm^-3. Using this multiple-peak RTD in series with a field-effect transistor load, a nine-state multivalued memory circuit is demonstrated     

Improving the peak current density of resonant tunneling diode based on InP substrate

Resonant tunneling diodes (RTD) have the potential for compact and coherent terahertz (THz) sources operating at room temperature, but their low output power severely restricts their application in THz frequency range. In this paper, two methods are adopted to increase the peak current of RTD for enhancing its output power. First, different metal contact systems (including Pt/Ti/Pt/Au and AuGe/Ni/Au) for RTD contact are introduced, and a higher current of RTD with Pt/Ti/Pt/Au contact demonstrates the superior contact characteristic of Pt/Ti/Pt/Au contact system. Second, the double barrier structure (DBS) of RTD is well designed to further improve the characteristic of RTD, and a high peak current of 154 kA/cm² is achieved at room temperature. The improved peak current is very beneficial for increasing the output power of RTD oscillator.     

Role of structure sizes in determining the characteristics of the resonant tunneling diode

Using the Wigner function formalism, we study the effects of structural parameters on the DC I-V characteristics and on the large-signal transient response of the resonant tunneling diode. We model two types of structures of GaAs/Al_xGa_1-xAs; first, with symmetric barriers ranging from 3 to 8 nanometers in thickness separated by a 5 nanometer well, and second with a well varying from 3 to 8 nanometers between 3 nanometer barriers. Experimental variation of the barrier thickness and height changes the peak-to-valley ratio in the I-V curve, as predicted by elementary models of tunneling structures. This stems directly from the changes in tunneling probabilities. For the DC studies, we show that the peak-to-valley ratio in the I-V curve is a function of the resonance width, which depends both on the well and barrier thickness. The location of the peak on the I-V curve depends on the location of the resonant energy, which is a function of the well width. Transient switching behavior is compared to earlier numerical studies of tunneling times of wave packets. Charge storage stabilizes the position of the resonant state, thus damping the transients. Consequently, wider barriers yield faster transient settling times, in agreement with the tunneling time results which predicted longer charge storage times for thicker barriers.     

共振隧穿二极管的设计和研制

用分子束外延在半绝缘砷化镓上生长两垒一阱结构,制成RTD单管。经过材料生长设计、工艺设计和版图设计几方面的改进,测得最高振荡频率已达54GHz。     

Effect of radial growth rate variation on resonant tunneling diode current-Voltage characteristics

The uniformity of electronic device characteristics is dependent on the uniformity of the epitaxial material. Uniformity is particularly important for resonant tunneling diodes where small changes in well or barrier thickness can have profound effects on the diode current-voltage characteristics. The variability of these characteristics due to growth rate nonuniformity for epitaxial structures grown by molecular beam epitaxy has been documented and the magnitude of the thickness variations analyzed using photoluminescence and a theoretical model. An increase of 17 meV was observed in the quantum well ground state, corresponding to a 15% thinning of the well from the center to the edge of the substrate.     

Microwave detection using the resonant tunneling diode

An experimental and theoretical study in the use of a resonant tunneling diode (RTD) as a microwave detector, based on its small-signal equivalent circuit model, is presented. It is shown that the rectified current from the diode can be accurately predicted and that the diode can be operated as a reactive microwave detector which absorbs no microwave power. For this detection mode, a matching network which maximizes the applied AC voltage can be used     

An improved multipeak resonant tunneling diode model for nine-stateresonant tunneling diode memory circuit simulation

A simple Spice equivalent circuit model for simulating current-voltage (I-V) characteristics and logic operation waveforms of an eight-peak resonant tunneling diode is presented. The simulated results agreed well with experimental data measured from an eight-peak resonant tunneling diode device fabricated by Seabaugh's experiment. This is shown through PSpice simulation     

Two-band combined model of a resonant tunneling diode

A two-band combined model of a resonant tunneling diode, based on the semiclassical and quantum mechanical (the wave function formalism) approaches is proposed. The main specific feature of this model is the possibility of taking into account the interaction between different classical or quantum mechanical device regions with simultaneous consideration of the Γ-X intervalley scattering. It is shown that this model gives satisfactory agreement with the experimental data on the current-voltage characteristics and allows explanation of the plateau region in these characteristics within the stationary model.     

Pspice resonant tunneling diode models and application circuits

Using the analogue behavioural modelling capabilities of Pspice, the current–voltage characteristics and the large-signal equivalent circuit of a resonant tunneling diode are exploited to create a Pspice compatible model for the diode. The model is used, with very few other components, in the simulation of a number of circuit applications, including a sinusoidal wave generator, a frequency multiplier and three state logic circuits. The simulated circuit details, the related waveforms and three-state logic operations are described. The circuits are characterized mainly by their reduced complexity and ease of analysis.     

Unified AC model for the resonant tunneling diode

A physics-based model is shown to yield the small-signal equivalent circuit of the resonant tunneling diode (RTD) including an analytic expression for both the quantum inductance and capacitance. This model unifies previous models by Brown et al. for quantum inductance and by Lake and Yang for quantum capacitance, and extends the RTD SPICE model of Broekaert. The equivalent circuit has been fit to both current-voltage and microwave S-parameter measurements of AlAs-InGaAs-InAs-InGaAs-AlAs RTDs from 45 MHz to 30 GHz and over biases from 0 to 0.81 V. Good agreement between the model and measurement is shown.     

A triple-well resonant tunneling diode for multiple-valued logicapplication

A resonant tunneling diode with four potential barriers and three quantum wells was fabricated and applied to multiple-valued logic. The diode exhibited significant double negative resistance characteristics and operated as a triple stable device with a single voltage between 180 and 230 K     

Design of nanopipelined adder based on resonant tunneling diode

Due to the negative differential resistance exhibited by resonant tunneling diode (RTD), RTD is suited to implement the threshold gates and increases the functionality of a single gate. Recently, multi-threshold threshold gates (MTTGs) and generalized threshold gates (GTGs) have been proposed, which extend the circuit applications of RTDs. In this paper, a new RTD full adder structure with three logic modules is proposed. Based on this structure, four different adders are built with the combination of different module circuits based on MTTG and GTG. From the simulation results, one of the proposed circuits with GTG structure, namely FA_GG, has the best performance, which reduces 27.7–45.9% power-delay product value in comparison with the previous designs.     

Multibit resonant tunneling diode SRAM cell based on slew-rateaddressing

We propose and demonstrate a resonant-tunneling diode (RTD) based memory cell in which N bits are stored in a series combination of N RTDs without internal node contacts. The slew rate of an applied voltage signal determines the circuit switching dynamics and allows addressing of the bits. We verify slew rate dependent switching order of up to four series RTDs experimentally and through SPICE simulation incorporating a physics-based RTD model. The new addressing scheme allows N bits to be stored in a stack of N vertically integrated RTDs compared to log₂ (N) bits in previous demonstrations. We demonstrate a two-bit two-RTD static memory cell based on the new method     

太赫兹共振隧穿二极管探测器研究进展及应用

太赫兹波独特的性质使其在物理学、生物学、医疗诊断、无损检测、无线通信等领域有着广阔的应用前景。共振隧穿二极管(RTD)是一种基于量子隧穿效应的半导体器件,利用其负微分电阻和直流非线性特性,可以分别实现太赫兹波的产生和探测,近年来获得越来越多的关注。基于RTD的太赫兹探测器具有可室温工作、体积小、易集成、灵敏度高等特点,使其在未来短距离、超高速的太赫兹无线通信及万物互联等场景具备优势。本文将重点介绍太赫兹RTD探测器的研究进展及其应用进展,并对后续技术发展进行展望。     

InP基共振隧穿二极管太赫兹振荡器的设计与实现

利用InP基共振隧穿二极管（RTD）和加载硅透镜的片上天线设计实现了超过1 THz的振荡器。采用Silvaco软件对RTD模型进行仿真研究,分析了不同发射区掺杂浓度、势垒层厚度、隔离层厚度以及势阱层厚度等对器件直流特性的影响规律。对研制的RTD器件直流特性测试显示：峰值电流密度Jp为359.2 kA/cm²,谷值电流密度Jv为135.8 kA/cm²,峰谷电流比PVCR为2.64,理论计算得到的器件最大射频输出功率和振荡频率（fmax）分别为1.71 mW和1.49 THz。利用透镜封装的形式对采用Bow-tie片上天线和RTD设计的太赫兹振荡器进行封装,测试得到振荡频率超过1 THz,输出功率为2.57μW,直流功耗为8.33 mW,是国内首次报道超过1 THz的振荡器。     

A multiple-state memory cell based on the resonant tunneling diode

The device consists primarily of several molecular-beam-epitaxy (MBE-) grown GaAs/(AlGa)As resonant tunneling diodes connected in parallel. This device exhibits multiple peaks in the I-V characteristic. When a load resistor is connected, the circuit can be operated in a multiple stable mode. With this concept, implementation of three-state and four-state memory cells are made. In the three-state case the operating points at voltages V₀=0.27 V , V₁=0.42 V, and V₂=0.53 V represent the logic levels 0, 1, and 2. Similarly for the four-state memory cell the logic levels voltages are V₀=0.35 V, V₁=0.42 V, V₂=0.54 V, and V ₃=0.59 V. A suggestion of an integrated device structure using this concept is also presented     

Integration of a resonant tunneling diode and an optical communications laser

We report on the first integration of a resonant tunneling diode and an optical communications laser operating at around 1.5 /spl mu/m. We demonstrate its low-frequency bistable operation and model its electrical characteristics.     

Optical control of resonant tunneling diode monolithically integrated with PIN photodiode

Optical control of the resonant tunneling characteristics of an integrated optoelectronic device with a monolithic integrated double-barrier/PIN structure is studied. Optical switching of the bistable resonant tunneling state and optical injection locking of a resonant tunneling oscillator at 1 GHz are demonstrated.     

倍增型共振隧穿弱光探测器的噪声性能研究

对倍增型共振隧穿弱光探测器(RTDPD,resonant tunneling diode as photodetector)的噪声性能 进行研究。设计了具有倍增区的RTDPD结构。对探测器电流-电压(I-V) 特性的模拟发现,加入倍增区 以后探测器的光电流和暗电流均被放大,其峰值电流增大了1.7倍。 对RTDPD的噪声分布模拟发 现,1/f噪声比散粒噪声和热噪声高出10 个数量级左右。对倍增 区的电场强度和过剩噪声因子进行了模拟, 并计算了过剩噪声的功率谱密度。分析了倍增型RTDPD的总噪声,并对有、无倍增区时RTDPD 的噪声等 效功率进行了计算。结果显示,倍增区引入的噪声不仅不会影响探测器有效信号的提取,而 且提高了探测器响应弱光的能力。