InP-base resonant tunneling diodes

We have fabricated Ino.53Ga0.47As/AlAs/InP resonant tunneling diodes (RTDs) based on the air-bridge technology by using electron beam lithography processing. The epitaxial layers of the RTD were grown on semiinsulating (100) InP substrates by molecular beam epitaxy. RTDs with a peak current density of 24.6 kA/cm2 and a peak-to-valley current ratio of 8.6 at room temperature have been demonstrated.     

InP基共振遂穿二极管器件（RTD）研究

我们在实验中对InGaAs/AlAs/InP共振遂穿二极管（RTD）材料结构进行了优化设计,并用MBE设备在(100)半绝缘InP单晶片上生长了RTD外延材料。我们采用电子束光刻工艺和空气桥互连技术,制作了InP基RTD器件。并在室温下测试了器件的电学特性：峰值电流密度24.6kA/cm2,峰谷电流比(PVCR)为8.6。     

Combined two-band models of resonant tunneling diodes

A satisfactory agreement between calculated voltage-current characteristics of GaAs/AlAs and Si/SiGe heterostructure resonant tunneling diodes and experimental data was obtained by using combined two-band models based on semiclassical and quantum-mechanical approaches. A high sensitivity of the characteristics of GaAs/AlAs-based devices to factors such as the transverse wave vector, changes of the heterostructure??s X-conduction band minimum, the surface charge density on heterointerfaces, and G-X intervalley scattering, is shown.     

Multivalued SRAM cell using resonant tunneling diodes

A multivalued SRAM cell using a vertically integrated multipeak resonant tunneling diode (RTD) pair is described. Two RTDs in series can have 2N+1 stable states. With this concept, a five-stable-state memory cell has been implemented with two 2-peak RTDs. Several designs are presented for a high-speed static random access multivalued memory using the folding characteristics of RTDs. The different designs are described and studied by comparing their power consumption under different conditions of device parameters and switching speed. The authors show that the proposed memory cell using a pair of multipeak RTDs yields the best result from the standpoint of size, power dissipation, and speed among the RTD memory cells discussed     

Sidewall spacer defined resonant interband tunneling diodes

We report on a contacting and fabrication scheme for a sub-500 nm InAs/AlSb/GaSb resonant interband tunneling diode (RITD) without using any fine-line lithography. Epitaxial regrowth on patterned substrates combined with sidewall spacer technology is used to define the device dimensions. During regrowth, the crystal facet termination obtained by choosing the appropriate orientation for the device is utilized to make electrical contact to the device in the desired directions and to isolate the device in all other directions. The concept, fabrication process, current-voltage characteristics of the device, and a comparison with RITDs fabricated in a conventional manner are reported.     

Analysis of defect-assisted tunneling based on low frequency noise measurements of resonant tunnel diodes

An experimental apparatus and procedure using noise measurement techniques have been developed in order to identify conduction mechanisms in RTDs due to defect assisted tunneling. The theory of noise measurements is discussed as the basis for the appropriate modelling of RTD noise data. The activation energies and capture cross-sections have been determined in a typical RTD for each of three distinct trap levels. A conjecture is made as to the physical location of the traps. This interpretation yields qualitative behavior consistent with the known bias and temperature dependence of the experimental results.     

Power and stability limitations of resonant tunneling diodes

Stability criteria for resonant tunneling diodes are investigated. Details of how extrinsic elements, such as series inductance and parallel capacitance, affect the stability are presented. A GaAs/AlAs/InGaAs/AlAs/GaAs double-barrier diode is investigated, showing the effect of different modes of low-frequency oscillation and the extrinsic circuit required for stabilization. The effect of device stabilization on high-frequency power generation is described. The main conclusions of the paper are: (1) stable resonant tunneling diode operation is difficult to obtain, and (2) the circuit and device conditions required for stable operation greatly reduce the amount of power that can be produced by these devices     

Static frequency divider featuring reduced circuit complexity byutilizing resonant tunneling diodes in combination with HEMTs

A static frequency divider constructed with resonant tunneling diodes (RTDs) in combination with HEMTs is proposed and demonstrated. The circuit complexity is reduced drastically. The proposed circuit is fabricated using InP-based RTD/HEMT monolithic integration technology. Proper operation is demonstrated at room temperature by a quasi-static test pattern. The circuit includes two sub-circuits which behave like D-latches. Each sub-circuit consists of only three components. This number of components is one fifth of that required to construct a D-latch using conventional SCFL technology. The strong nonlinear I-V characteristics of RTD's are fully utilized for this reduction     

Characterization of resonant tunneling diodes for microwave andmillimeter-wave detection

The authors report on the direct detection capabilities of resonant tunneling diodes in the 10-100 GHz range. An open circuit voltage sensitivity of 1750 mV/mW (in Ka-band) was measured. This is higher than the sensitivity of comparatively based commercially available solid-state detectors. The detector properties are a strong function of diode bias and the measured tangential signal sensitivity (-32 dBm at Ka-band with 1-MHz bandwidth) and the dynamic range (25 dB) of the diode are smaller compared to other solid-state detectors     

Two-dimensional simulation for resonant tunneling transistor

A new two-dimensional device simulation for the resonant tunneling transistor is presented. In the simulation, the one-dimensional Schrodinger equation is solved for the intrinsic area of the transistor and the conventional two-dimensional drift-diffusion equations are solved for the extrinsic part. Both equations are coupled with the carrier generation-recombination term in the drift-diffusion equations. In addition, the Poisson equation is also solved self-consistently with them to take the charge distribution effect into account. The two-dimensional simulator has been successfully applied to the analysis of a resonant tunneling transistor and it was found that the current-voltage characteristics sensitively depend on the base resistance. This means that a two-dimensional treatment of the voltage drop in the base region is essential for an accurate simulation     

Space-charge effects and ac response of resonant tunneling double-barrier diodes

We analyse theoretically the small-signal ac response of a resonant tunneling double-barrier semiconductor diode using the sequential tunneling approach. Electrostatic feedback effects due to space charge buildup in the quantum well are included in the analysis. The results are expressed in terms of an equivalent circuit which is used to interpret measurements of the capacitance of an asymmetric double-barrier structure at low frequencies (< 1 MHz). The frequency dependence of the real and imaginary parts of the impedance at microwave frequencies are also discussed.     

High performance AlAs/GaXIn1-xAs resonant tunneling diodes by metalorganic chemical vapor deposition

We report on AlAs/Ga_xJn_1−xAs (x = 0.47) quantum well heterostructures grown by metalorganic chemical vapor deposition (MOCVD) on InP substrates. Heterostructure quality was evaluated by high resolution x-ray diffraction for various growth conditions. Double barrier quantum well heterostructures were grown and processed into resonant tunneling diodes (RTDs). Room temperature electrical measurements of the RTDs yielded maximum peak to valley current ratios of 7.7 with peak current density of 96 kA/cm² and 11.3 with peak current density of 12 kA/cm², for devices grown by atmospheric and low pressure MOCVD, respectively.     

QDRTD单光子探测技术

量子信息技术的发展对单光子探测器提出了更高的性能要求,新型的量子点单光子探测器展现出了很好的性能和发展潜力。研究了一种基于量子点共振隧道二极管(QDRTD)的单光子探测器,介绍了QDRTD的基本结构和原理,重点对其内部电子传输特性和I-V特性进行了分析,并进行了结构优化,可满足单光子探测中多种波长选择的需求,为QDRTD多波长单光子探测的光子响应特性、探测效能等研究奠定了基础。同时,分析结果表明:QDRTD单光子探测器在光子响应、暗电流、波长选择等多个方面都具备很好的特性,具有广阔的应用前景。     

A self-latching A/D converter using resonant tunneling diodes

A high-speed analog-to-digital (A/D) converter based on the resonant tunneling diode (RTD) is described. This A/D converter takes advantage of the folding characteristic of the RTD to reduce circuit complexity. The speed of the A/D converter is improved by the fast latching action of the RTD digitizer. Simulations show that the 4-B A/D converter can have a sampling rate of several gigahertz     

A novel A/D converter using resonant tunneling diodes

A large-signal resonant tunneling diode (RTD) model is used to simulate the performance of a 2-b A/D converter. Results from the theoretical analysis, the breadboard circuit demonstration, and the SPICE3 simulation are discussed. It is shown that the unique folding characteristics of the vertically integrated RTD greatly reduce the complexity of the A/D converter circuit, making analog-to-digital conversion at tens-of-gigahertz rates possible     

0.1 μm Schottky-collector AlAs/GaAs resonant tunneling diodes

The Schottky-collector resonant tunneling diode (RTD) is an RTD with the normal N+ collector and ohmic contact replaced by a Schottky contact, thereby eliminating the associated parasitic resistance. With submicron Schottky contact dimensions, the remaining components of the parasitic series resistance can be greatly reduced, resulting in an increased maximum frequency of oscillation, f_max. AlAs/GaAs Schottky-collector RTDs were fabricated using 0.1 μm T-gate technology developed for high electron mobility transistors. From their measured dc and microwave parameters, and including the effect of the quantum well lifetime, f_max=900 GHz is computed     

Considerations and simulations of subfrequency excitation of seriesintegrated resonant tunneling diodes oscillator

A subfrequency pulse initiation of an oscillator of two series-integrated RTD's is considered and simulated. A voltage-dependent current source is adopted to separate the input and output power to represent a circulator in simulations. Simulations show, for example, a 100 GHz integrated RTD oscillator can be excited by a 50 GHz pulse with about 1 ns decay time (a characteristic decay time of 0.2 ns) without the DC instability problem, while a voltage ramp of 1 ns rise or fall time is far too slow to initiate such an oscillator. The mechanism that RTD's are driven by subfrequency into the negative differential resistance (NDR) from the positive differential resistance (PDR) is analyzed in detail. A preliminary analysis of the transition from 50-100 GHz oscillation is also presented     

RF performance and modeling of Si/SiGe resonant interband tunneling diodes

The RF performance of two different Si-based resonant interband tunneling diodes (RITD) grown by low-temperature molecular beam epitaxy (LT-MBE) were studied. An RITD with an active region of B /spl delta/-doping plane/2 nm i-Si/sub 0.5/Ge/sub 0.5//1 nm i-Si/P /spl delta/-doping plane yielded a peak-to-valley current ratio (PVCR) of 1.14, resistive cutoff frequency (f/sub r0/) of 5.6 GHz, and a speed index of 23.3 mV/ps after rapid thermal annealing at 650/spl deg/C for 1 min. To the authors' knowledge, these are the highest reported values for any epitaxially grown Si-based tunnel diode. Another RITD design with an active region of 1 nm p+ Si/sub 0.6/Ge/sub 0.4//B /spl delta/-doping plane/4-nm iSi/sub 0.6/Ge/sub 0.4//2 nm i-Si/P /spl delta/-doping plane and annealed at 825/spl deg/C for 1 min had a PVCR of 2.9, an f/sub r0/ of 0.4 GHz, and a speed index of 0.2 mV/ps. A small signal model was established to fit the measured S/sub 11/ data for both device designs. Approaches to increase f/sub r0/ are suggested based on the comparison between these two diodes. The two devices exhibit substantially different junction capacitance/bias relationships, which may suggest the confined states in the /spl delta/-doped quantum well are preserved after annealing at lower temperatures but are reduced at higher temperature annealing. A comprehensive dc/RF semi-physical model was developed and implemented in Agilent advanced design system (ADS) software. Instabilities in the negative differential resistance (NDR) region during dc measurements were then simulated.     

An assessment of potential nonlinear circuit models for thecharacterization of resonant tunneling diodes

The intrinsically fast process of resonant tunneling through double barrier heterostructures along with the existence of negative differential resistance in the current-voltage characteristic of these structures has led to their implementation as sources for high frequency electromagnetic energy. While sources based upon resonant tunneling diodes (RTDs) have produced frequency of oscillations up to 712 GHz, only microwatt levels of performance has been achieved above 100 GHz. Since stability criteria plays critical role in determining the deliverable power of any oscillator, a physically accurate equivalent-circuit model for the RTD is extremely important for optimizing the dynamics of the device-cavity package. This study identifies a distinctly new equivalent circuit model for characterizing the modes of oscillation in RTD-based sources. Specifically, in order to exhibit the fundamental self-oscillations and the overall I-V characteristics (plateau structure and hysteresis) observed experimentally, an accurate circuit model of the RTD must incorporate: (i) a quantum-well inductance which directly chokes the nonlinear conductance and, (ii) a nonlinear access resistance, associated with the accumulation of charge in the injection region of the double barriers, with a nonlocal dependence on the bias across the double barrier structure     

InAs/AlSb/GaSb resonant interband tunneling diodes andAu-on-InAs/AlSb-superlattice Schottky diodes for logic circuits

Integrated resonant interband tunneling (RIT) and Schottky diode structures, based on the InAs/GaSb/AlSb heterostructure system, are demonstrated for the first time. The RIT diodes are advantageous for logic circuits due to the relatively low bias voltages (~100 mV) required to attain peak current densities in the mid-10⁴ A/cm ² range. The use of n-type InAs/AlSb superlattices for the semiconducting side of Schottky barrier devices provides a means for tailoring the barrier height for a given circuit architecture. The monolithically integrated RIT/Schottky structure is suitable for fabrication of a complete diode logic family (AND, OR, XOR, INV)