利用空气桥技术实现InP基共振遂穿二极管器件

优化设计了InGaAs/AlAs/InP共振遂穿二极管（RTD）材料结构,并用MBE设备在（100）半绝缘InP单晶片上生长了RTD外延材料。利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78kA/cm2,峰谷电流比（PVCR）为7.8。利用空气桥互连技术实现该类器件,在国内尚属首次。     

InP基RTD/HEMT集成的几个关键工艺研究

用MBE设备在半绝缘的InP衬底上依次生长高电子迁移率晶体管(HEMT)外延材料和共振遂穿二极管(RTD)外延材料,在此材料结构基础上研究和分析了RTD与HEMT器件单片集成工艺中的隔离工艺、欧姆接触工艺、HEMT栅挖槽工艺和空气桥工艺等几步关键工艺,给出了这些工艺的相关参数。利用上述工艺成功地制作了RTD和HEMT器件,并在室温下分别测试了RTD器件和HEMT器件的电学特性。测试表明:在室温下,RTD器件的峰电流密度与谷电流密度之比(PVCR)为3.66;HEMT器件的最大跨导约为370 mS/mm,在Vds=1.5 V时的饱和电流约为391 mA/mm。这将为RTD与HEMT的单片集成研究奠定工艺基础。     

GaAs基共振遂穿二极管的材料结构研究

用分子束外延技术在半绝缘GaAs衬底上生长了三种不同材料结构的RTD.主要针对阱结构进行了对比设计,然后对设计结构进行了常温下的I-V特性测试,测试结果中器件的PVCR值最高达到了6,V<,p>降低到了0.41 V.同时常温下测试了其中一种设计结构的敏感单元在四种不同发射极面积下的I-V特性曲线.最后对器件阱结构和发射...     

共振隧穿二极管的材料结构设哥——共振隧穿器件讲座（5）

在系统细致分析RTD材料结构参数与器件特性参数关系的基础上，确立了RTD材料结构的设计原则和设计方法，并对以SI—GaAs为衬底的RTD分子束外延（MBE）材料生长结构进行了设计。所研制出的RTD参数实测结果证实了此设计方法是正确的。     

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。     

用于高速电路的InP基共振隧穿二极管制作

在InP衬底上采用感应耦合等离子体刻蚀技术制备了高性能的AlAs/In0.53Ga0.47As/InAs共振隧穿二极管.正向偏压下PVCR=7.57,Jp=39.08kA/cm2;反向偏压下PVCR=7.93,Jp=34.56kA/cm2.在未去除测试电极和引线等寄生参数影响下,面积为5μm×5μm的RTD的阻性截止频率为18.75GHz.最后对非对称的I-V特性进行了分析讨论.     

共振隧穿二极管研究进展

简要评述共振隧穿二极管（ＲＴＤ）器件研究进展。重点探讨以下问题：为什么ＲＴＤ研究经久不衰？器件理论模型达到何等水平？器件特性、结构和材料方面有哪些关键？围绕这些问题,介绍了有关基本概念,对ＲＴＤ器件物理模型和特性近来的研究成果和前景进行了分析,并提要性地和同类的其它量子器件作了比较。     

纳米电子器件-高峰值峰谷电流比InP基共振隧穿二极管的实现

利用分子束外延技术研制出InP基IhAs/In0.53Ga0.47As/AlAs共振隧穿二极管,其中势垒为10个单分子AlAs,势阱由8个单分子层In0.53Ga0.47As阱和4个单分子层InAs子阱组成.室温下峰值电流密度接近3kA/cm2,峰和谷的电流密度比率达到19.     

纳米电子器件-高峰值峰谷电流比InP基共振隧穿二极管的实现

利用分子束外延技术研制出InP基IhAs/In0.53Ga0.47As/AlAs共振隧穿二极管,其中势垒为10个单分子AlAs,势阱由8个单分子层In0.53Ga0.47As阱和4个单分子层InAs子阱组成.室温下峰值电流密度接近3kA/cm2,峰和谷的电流密度比率达到19.     

共振隧穿二极管的材料结构设计——共振隧穿器件讲座(5)

在系统细致分析RTD材料结构参数与器件特性参数关系的基础上,确立了RTD材料结构的设计原则和设计方法,并对以SI-GaAs为衬底的RTD分子束外延(MBE)材料生长结构进行了设计。所研制出的RTD参数实测结果证实了此设计方法是正确的。     

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.     

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.     

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.     

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。     

Development of a simple two-step lithography fabrication process for resonant tunneling diode using air-bridge technology

This article reports on the development of a simple two-step lithography process for double barrier quantum well (DBQW) InGaAs/AlAs resonant tunneling diode (RTD) on a semi-insulating indium phosphide (InP) substrate using an air-bridge technology. This approach minimizes processing steps, and therefore the processing time as well as the required resources. It is particularly suited for material qualification of new epitaxial layer designs. A DC performance comparison between the proposed process and the conventional process shows approximately the same results. We expect that this novel technique will aid in the recent and continuing rapid advances in RTD technology.     

High frequency simulation of resonant tunneling diodes

The small and large-signal response of the resonant tunneling diode at high-frequencies is studied using a quantum simulator. The Poisson and Schrodinger equations are solved self-consistently for each harmonic using the harmonic balance technique. This ensures that the total current, consisting of the displacement plus conduction currents, is conserved across the device for each harmonic. The RTD exhibits an increased capacitance in the negative differential conductance (NDC) region in agreement with experimental data. As recently proposed this capacitance increase results from the formation of an emitter well capacitor when the well discharges. The derivation of the RTD capacitance from a quasi-static analysis using the differential variation of the de charge in the RTD is shown to be not applicable because the RTD well charges through the cathode but discharges through the anode. The frequency dependence of the conductance and susceptance is similar to reported experimental data. A large frequency dependence of the admittance is only observed when the RTD is biased in the negative differential conductance (NDC) region. These calculations predict an effective reduction of the RTD conductance and capacitance at high-frequency in the NDC region. This effect can be modeled using a quantum inductance in series with the negative resistance of the RTD as recently proposed. Due to the simultaneous reduction of both the conductance and the capacitance at high-frequency in the NDC region the maximum frequency of oscillation does not differ much from its estimate using the low frequency conductance and capacitance. The large-signal response at high-frequency of an RTD biased in the negative differential region is also presented in this paper. The large-signal negative-conductance is shown to decrease with both increasing frequency and ac voltage     

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     

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     

Piezoresistive effect in GaAs/InxGa1−xAs/AlAs resonant tunneling diodes for application in micromechanical sensors

The current–voltage characteristics of GaAs/In_xGa_1−xAs/AlAs resonant tunneling diodes (RTDs) are a function of stress, and the current–voltage changes of RTDs with stress are attributed to the piezoresistive effect in RTDs. In order to study the piezoresistive effect in RTDs for application in micromachined mechanical sensors, the beam-mass structure based on RTDs is designed, fabricated and tested by the Wheatstone bridge test circuit. The test results show that the piezoresistive sensitivity of RTDs can be adjusted through the bias voltage, and the maximal piezoresistive sensitivity of RTDs with bias voltage at 0.618 V is 7.61×10⁻¹¹ Pa⁻¹, which is two orders higher than the minimal piezoresistive sensitivity (2.03×10⁻¹³ Pa⁻¹) of RTDs with bias voltage at 0.656 V, and is also higher than the piezoresistive sensitivity of silicon material (5.52×10⁻¹¹ Pa⁻¹).