Low noise oscillator approaches at 140 GHz

Conclusion It was demonstrated that approaches towards oscillators with sufficient noise performance familiar up to frequencies of 100 GHz can be applied at 140 GHz with only minor modifications.Mostly due to the limitations imposed by the available InP Gunn diodes the power levels reached with second harmonic mode operation were less than at 94 GHz with GaAs devices. The two approaches employing IMPATT diodes deliver substantial output power at D-band. Which one is preferrable will be dependent on the application.     

Generation of Submillimeter-Wave Radiation with GaAs Tunnett Diodes and InP Gunn Devices in a Second or Higher Harmonic Mode

Efficient second-harmonic power extraction was demonstrated recently with GaAs tunnel injection transit-time (TUNNETT) diodes up to 235 GHz and with InP Gunn devices up to 325 GHz. This paper discusses the latest theoretical and experimental results from second-harmonic power extraction at submillimeter-wave frequencies and explores the potential of using power extraction at higher harmonic frequencies to generate continuous-wave radiation with significant power levels at frequencies above 325 GHz. Initial experimental results include output power levels of more than 50 W at 356 GHz from a GaAs TUNNETT diode in a third-harmonic mode and at least 0.2–5 W in the frequency range 400–560 GHz from InP Gunn devices in a third or higher harmonic mode. The spectral output of these submillimeter-wave sources was analyzed with a simple Fourier-transform terahertz spectrometer and, up to 426 GHz, with a spectrum analyzer and appropriate harmonic mixers. Initial experimental results from a GaAs/AlAs superlattice electronic device at D-band (110–170 GHz) and J-band (170–325 GHz) frequencies are also included.     

Heterogeneous integration of InP HEMTs on quartz wafer using BCB bonding technology

Heterogeneous integrated InP high electron mobility transistors(HEMTs)on quartz wafers are fabricated successfully by using a reverse-grown InP epitaxial structure and benzocyclobutene(BCB)bonding technology.The channel of the new device is In_0.7Ga_0.3As,and the gate length is 100 nm.A maximum extrinsic transconductance gm,max of 855.5 mS/mm and a maximum drain current of 536.5 mA/mm are obtained.The current gain cutoff frequency is as high as 262 GHz and the maximum oscillation frequency reaches 288 GHz.In addition,a small signal equivalent circuit model of heterogeneous integration of InP HEMTs on quartz wafer is built to characterize device performance.     

Investigation of chlorine-based etchants in wet and dry etching technology for an InP planar Gunn diode

Mesa etching technology is considerably important in the Gunn diode fabrication process. In this paper we fabricate InP Gunn diodes with two different kinds of chlorine-based etchants for the mesa etching for comparative study. We use two chlorine-based etchants, one is HCl-based solution (HCl/H 3 PO 4 ), and the other is Cl 2 -based gas mixture by utilizing inductively coupled plasma system (ICP). The results show that the wet etching (HCl-based) offers low cost and approximately vertical sidewall, whilst ICP system (Cl 2 -based) offers an excellent and uniform vertical sidewall, and the over-etching is tiny on the top and the bottom of mesa. And the fabricated mesas of Gunn diodes have average etching rates of ～ 0.6 μm/min and ～ 1.2 μm/min, respectively. The measured data show that the current of Gunn diode by wet etching is lower than that by ICP, and the former has a higher threshold voltage. It provides a low-cost and reliable method which is potentially applied to the fabrication of chip terahertz sources.     

Submillimeter-wave heterodyne spectroscopy with a compact solid state radiometer

A compact, solid state submillimeter-wave heterodyne radiometer has been developed and was used to measure spectral characteristics of a water vapor jet in a space simulation chamber. Features of the 557 GHz water vapor line profile were observed in significantly greater detail than in previous experiments through an increased sensitivity and improved frequency resolution (600 kHz). The local oscillator of the radiometer consisted of a frequency multiplication chain which was driven by an InP Gunn oscillator at 92.6 GHz, and which contained a frequency tripler and harmonic mixer in cascade. The front end of the receiver had a noise temperature of 4500 K (DSB) at 555 GHz, consumed 3 W and weighed 3 kg. This advance in technology is particularly relevant to submillimeter-wave radiometry from a space-based platform.     

Experimental investigation of millimeter wave Gunn oscillator circuits in circular waveguides

Millimeter wave Gunn oscillator circuits using circular waveguides for 33–50 GHz and 75–110 GHz frequency bands are described. These oscillators are simpler to construct at millimeter wavelengths compared to the conventional rectangular waveguide circuits. The effect of various circuit parameters on the oscillator frequency and output power has been experimentally studied. The CW power and mechanical tuning range obtained from the circular waveguide Gunn oscillators are found to be comparable and sometimes even better than those obtained with conventional rectangular waveguide circuits using the same Gunn device.     

Planar oscillators for monolithic integration

Planar oscillators for monolithic millimeter-wave integrated circuits are considered, and a design based on a coplanar-waveguide resonator is described. Design data are obtained from simulation at 1 GHz. the resonator has a Q of 195 (50 when scaled to 100 GHz) and is mechanically tunable over a range of 12%. Combining this resonator with a Gunn diode, a model oscillator is obtained. Output is obtained quasi-optically through a transmitting antenna. Twenty one milliwatts of output at 4.5 GHz are obtained with high spectral purity. A 100 GHz monolithic planar oscillator based on this design should be possible.Research supported by the U.S. Army Research Office Contract DAAG29-79CO134, the National Science Foundation under Grant ECS-8116018, and the Joint Services Electronics Program (AFOSR Contract F49620-79-C-0178).     

A Gunn-Diode Active Leaky-Wave Frequency Scanning Antenna

A frequency tunable active leaky-wave scanning antenna using Gunn-diode voltage control oscillator (VCO) as source is developed. The frequency tuning controlled by changing either the varactor diode dc bias or the Gunn diode dc bias is demonstrated. The measured scanning angle of active antenna is close to 15 degree as the Gunn VCO frequency tuned from 12.58GHz to 12.98GHz. To excite the first higher order mode of the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the middle line of the microstrip leaky wave antenna. This is a prototype of frequency scanning antenna using two terminal device, which can be easily scaled up to millimeter wave frequency region.     

Optimized design of quasi-optical source-array of solid state source power combiner at frequency 100 GHz

It is determined for the structure of the source-array located in inner surface of input quasi-optical resonator operating at frequency 100GHz using Type WT5731 GaAs Gunn diodes made in P.R. China (fundamental frequency 50 GHz). An adaptable phase coupling has been achieved and RF output power exceeded the sum of the individual diode outputs by from three to seven times.     

Millimeter wave pulsed gunn oscillator for low chirp radar application at W-Band

Pulsed Gunn oscillator at 94 GHz has been developed using GaAs CW Gunn diode, by choosing a proper operating point and resonant circuit. Peak power output of 25 mw at 94 GHz with a pulse width of 2 microseconds and duty factor of 2% is achieved. Bias circuit oscillations are suppressed by rising the operating voltage alongwith other circuit considerations.     

Dynamic optical arbitrary waveform generation and detection in InP photonic integrated circuits for Tb/s optical communications

This article presents recent results in the development of optical arbitrary waveform generation (OAWG) technologies based on optical frequency combs and indium phosphide devices. A novel spectral-slice dynamic-OAWG approach and waveform shapers with customized spectral multiplexers and modulators, enable continuous generation of high fidelity optical waveforms accessing bandwidths in excess of 1 THz. We show results for two types integrated waveform shapers, a 100 GHz electrically controlled device with 10 channels spaced at 10 GHz and a 1 THz optically controlled device with 100 channels spaced at 10 GHz. Additionally, we include results from a 640 GHz waveform measurement device with 16 channels and 40 GHz spacing.     

Lasing from GaAs Gunn devices

Lasing from a GaAs Gunn device with a Fabry–Perot (F–P) cavity and a vertical-cavity structures are demonstrated. Light output-electric field characteristic of both F–P and vertical cavity structure Gunn device shows abrupt increase in light output above a negative differential resistance (NDR) threshold, implying cavity gain overcoming over loss. Electroluminescence (EL) spectra from the F–P Gunn device measured at 95 K show a significant spectral narrowing with increasing the applied voltage pulse width, indicative of monochromatic stimulated emission due to band-to-band recombination of impact-ionized carriers. The spectra from the vertical-cavity device are in accord with the cavity resonance as defined by the distributed Bragg reflectances (DBRs). The theoretical model on carrier generation via impact ionization inside the propagating space charge domains shows clearly that the built-up excess carrier density in the cavity indeed reaches the lasing threshold.     

Noise performance of an InP/InGaAs superlattice avalanche photodiode

The noise performance of an InP/InGaAs Superlattice Avalanche Photodiode (SL-APD) has been studied theoretically to examine its suitability as a detector in optical receiver units. The results indicate that the device which has a very large gain-bandwidth product (450 GHz) provides a high receiver sensitivity compared to conventional APD. The device also exhibits a very low value of excess noise factor which results in a high value of signal-to-noise ratio. The SL-APD is expected to find useful applications as a high sensitivity photodetector in long-haul fibre optic communication systems. For a digital system, the device exhibits a very low value of bit-error rate (BER) even at moderate gain.     

The design and manufacture of a notch structure for a planar InP Gunn diode

A planar InP-based Gunn diode with a notch doping structure is designed and fabricated for integration into millimeter-wave and terahertz integrated circuits.We design two kinds of InP-based Gunn diodes.One has a fixed diameter of cathode area,but has variable spacing between anode and cathode;the other has fixed spacing,but a varying diameter.The threshold voltage and saturated current exhibit their strong dependences on the spacing(10 μm-20 μm) and diameter(40 μm-60 μm) of the InP Gunn diode.The threshold voltage is approximately 4.5 V and the saturated current is in a range of 293 mA-397 mA.In this work,the diameter of the diode and the space between anode and cathode are optimized.The devices are fabricated using a wet etching technique and show excellent performances.The results strongly suggest that low-cost and reliable InP planar Gunn diodes can be used as single chip terahertz sources.     

High frequency characterisation of double drift region InP and GaAs diodes

Computer studies have been made on the high frequency characteristics of symmetrically doped flat profile double drift region (DDR) InP and GaAs impatts in the mm-wave (60–100 GHz) frequency band. The spatial distribution of high frequency negative resistance and reactance in the depletion layer of DDR devices and their admittance properties have been investigated. The results indicate that DDR InP impatts should have higher drift zone voltage drop, higher negative resistance and higher negative conductance compared to their GaAs counterparts designed for the same range of mm-wave frequencies. Furthermore, the negative resistance peak is larger in magnitude for InP impatts compared to that for GaAs impatts. It is thus observed that DDR InP impatts should be superior to their GaAs counterparts as regards mm-wave power generation with high conversion efficiency.     

单载流子传输的双异质结光敏晶体管探测器的研究

基于器件仿真器Atlas, 建立了InP/InGaAsP单向载流子传输的双异质结光敏晶体管(UTC-DHPT)的二维模型, 分析讨论了器件性能与外延结构参数的关系. 设计出同时具有高响应度(≥17.93 A/W)和高特征频率(≥121.68 GHz)的UTC-DHPT, 缓解了传统的异质结光敏晶体管光电探测器中探测效率和工作速度的矛盾. 关键词： 单向载流子 光敏晶体管 电流放大倍数 响应度     

A G-band terahertz monolithic integrated amplifier in 0.5-μm InP double heterojunction bipolar transistor technology

Design and characterization of a G-band(140–220 GHz) terahertz monolithic integrated circuit(TMIC) amplifier in eight-stage common-emitter topology are performed based on the 0.5-μm In Ga As/In P double heterojunction bipolar transistor(DHBT). An inverted microstrip line is implemented to avoid a parasitic mode between the ground plane and the In P substrate. The on-wafer measurement results show that peak gains are 20 dB at 140 GHz and more than 15-dB gain at 140–190 GHz respectively. The saturation output powers are-2.688 dBm at 210 GHz and-2.88 dBm at 220 GHz,respectively. It is the first report on an amplifier operating at the G-band based on 0.5-μm InP DHBT technology. Compared with the hybrid integrated circuit of vacuum electronic devices, the monolithic integrated circuit has the advantage of reliability and consistency. This TMIC demonstrates the feasibility of the 0.5-μm InGaAs/InP DHBT amplifier in G-band frequencies applications.     

Optimization of the UTC-PD Epitaxy for Photomixing at 340?GHz

We present a method to optimize the epitaxial layer structure of an InGaAs/InP uni-traveling-carrier photo-diode (UTC-PD) for continuous THz-wave generation. The design approach used is general in that it can be applied for any target frequency while this study focuses on 340 GHz. The photodiode epitaxy is modeled and optimized using a TCAD software implementing the hydrodynamic semiconductor equations. This physical device model was found to be in good agreement with reported experimental results. It is shown that the UTC-PD can generate ~1 mW at 340 GHz by choosing the optimum absorption layer and collection layer thicknesses.     

A novel millimeter wave gunn oscillator

It is described that the design, configuration and the performance of a novel millimeter wave Gunn oscillator stabilized by external cavity and temperature compensation in this paper. The frequency stability is 3.6 × 10⁻⁶ at 52 GHz over the teperature range from −10 to 50 °C. An output power of more than 100mW has been obtained in the frequency range from 51.5 to 52.8 GHz. This research work was supported by National Natural science Foundation and Electronic Industry Ministry of P. R. China.     

Hot electron injector Gunn diode for advanced driver assistance systems

This paper reviews the main aspects of the design, fabrication and characterization of GaAs Gunn diodes intended to be used in advanced driver assistance systems. The corresponding Gunn diode based oscillators operate at the microwave frequency of 77 GHz and deliver an output power up to 19.2 dBm (83.2 mW). To fulfill the high demands of the automotive industry, temperature stability and a high grade of frequency purity, the Gunn diode structure includes a hot electron injector. This is based on the heteroepitaxy of a graded gap Al_xGa_1-xAs layer and an adjacent thin highly doped GaAs layer. The hot electron injector properties are investigated using dc and rf electrical measurements, including the temperature influence as well. Specific production related data of the cavity oscillators using our Gunn diodes are presented. New alternatives, such as the resonant tunneling emitter as a hot electron injector and the Gunn diode based MMIC as oscillator, are introduced. PACS 85.30.-z; 73.40.-c; 07.57.Hm; 84.30.Ng; 85.30.Fg