GaN基肖特基势垒二极管结构优化研究进展

作为宽禁带半导体器件,GaN基肖特基势垒二极管(SBD)有耐高压、耐高温、导通电阻小等优良特性,这使得它在电力电子等领域有广泛应用。本文首先综述了SBD发展要解决的问题;然后,介绍了GaN SBD结构、工作原理及结构优化研究进展;接下来,总结了AlGaN/GaN SBD结构、工作原理及结构优化研究进展,并着重从AlGaN/GaN SBD的外延片结构、肖特基电极结构以及边缘终端结构等角度,阐述了这些结构的优化对AlGaN/GaN SBD性能的影响;最后,对器件进一步的发展方向进行了展望。     

Barrier height enhancement and temperature dependence of the electrical characteristics of Al Schottky contacts on p-GaAs with organic Rhodamine B interfacial layer

In this work, two types of Schottky barrier diodes (SBDs) with and without Rhodamine B interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the Rhodamine B interfacial layer on the main electrical parameters. It was seen that the barrier height (BH) value of 0.78 eV calculated for the Al/Rhodamine B/p-GaAs device was higher than the value of 0.63 eV of the conventional Al/p-GaAs Schottky diodes. It has been observed that the Rhodamine B film increases the effective BH by influencing the space charge region of GaAs. The main diode parameters such as the ideality factor (n) and zero-bias BH of SBD with Rhodamine B interfacial layer were found to be strongly temperature dependent and while the BH decreases, the ideality factor increases with decreasing temperature. It has been concluded that the temperature dependent characteristic parameters for Al/Rhodamine B/p-GaAs SBDs can be successfully explained on the basis of thermionic emission (TE) mechanism with Gaussian distribution of the barrier heights.     

A 119 GHz planar Schottky diode mixer for a space application

A planar single-ended GaAs Schottky diode mixer has been designed, built, and tested at 119 GHz. The mixer front end includes also a waveguide filter for image rejection, and a temperature compensated ring filter. Measurements at room temperature showed a conversion loss of 7 dB and a noise temperature of 900 K (SSB). At 100 K the measured noise temperature of the mixer was 500 K (SSB).     

A Very Low-Noise Integrated 3MM-Wave Schottky Diode Mixer and PHEMT IF Amplifier

An integrated 3mm-wave Schottky diode mixer and pseudomorphic high-electron-mobility transistor (PHEMT) IF amplifier with record noise performance at room temperature is described. The design has shown the room-temperature double-sideband (DSB) receiver noise temperature T_R^DSB of 190 K at 100 GHz due to a very low conversion loss in the full-height waveguide mixer and an ultra-low noise of the PHEMT IF amplifier. The receiver noise temperature has been reduced by a factor of 1.5 in comparison with the best previously reported 3mm-wave Schottky diode mixer receiver.     

GaAs Schottky devices for submillimeter wavelengths

Conclusion The above analyses assume the absence of excess noise in the Schottky barrier mixer diode. Achievement of such a condition is dependent not only on the absence of interfacial stress in the device structure, but also on device surface properties. Reduction of excess noise caused by these two mechanisms is discussed by Sherrill, et al.,⁽¹⁰⁾ and Kattman, et al.⁽¹¹⁾ Minimum conversion loss in the THz range occurs for mixer diode with the smallest possible junction capacitance. This capacitance can be reduced along with the R_s, C_j(0) product by decreasing the device area and increasing the active layer impurity concentration. It was shown above that this impurity concentration increase will (a) permit higher frequency of operation, (b) cause a lower intrinsic conversion loss, and (c) be responsible for an increase in mixer diode I–V slope parameter, V₀. The only potentially negative effect comes from (c), but the analysis reviewed in the last section shows that an increase in V₀ has a minimal effect on mixer noise temperature for terahertz range operation. Experimental results of Dr. H. P. Röser⁽¹²⁾ to frequencies as high as 2.5 THz are in agreement with these predictions.It is thus concluded on the basis of the above four analyses of device mixer noise temperature and conversion loss that reasonable Schottky barrier mixer diode operation can be expected to at least 10 THz.This work was supported in part by the National Science Foundation under Grant ECS-8412477     

AN UNCOOLED VERY LOW NOISE SCHOTTKY DIODE RECEIVER FRONT-END FOR MIDDLE ATMOSPHERIC OZONE AND CARBON MONOXIDE MEASUREMENTS

The paper describes an uncooled front-end of the Schottky diode receiver system, which may be applied for observations of middle atmospheric ozone and carbon monoxide thermal emission lines at frequencies 110.8 GHz and 115.3 GHz, respectively. The mixer of the front-end has utilized high-quality Schottky diodes that allowed us to reduce the mixer conversion loss. The combination of the mixer and an ultra-low-noise IF amplifier in the one integrated unit has resulted in double-sideband (DSB) receiver noise temperature of 260 K at a local oscillator (LO) frequency of 113.05 GHz in the instantaneous IF band from 1.7 to 2.7 GHz. This is the lowest noise temperature ever reported for an uncooled ozone receiver system with Schottky diode mixers.     

0.34 THz无线通信收发前端

描述了一种基于肖特基二极管技术的0.34 THz无线通信收发前端。该前端采用超外差结构,由0.34 THz谐波混频器、0.17 THz本振8倍频链和偏置电路组成。0.34 THz谐波混频器基于反向并联肖特基二极管,可以实现信号的上变频发射和下变频低噪声检测。0.17 THz本振8倍频链由三级二倍频及驱动放大链路组成,可将20~22.5 GHz信号倍频至0.16~0.18 THz,为混频器提供5~10 dBm左右的本振信号。实验测试结果表明:该前端用于信号发射时,在0.34 THz频点的饱和输出功率为-14.58 dBm;用于信号检测时,最低单边带(SSB)变频损耗为10.0 dB,3 dB中频带宽约30 GHz。限于测试条件,未能测试前端接收噪声温度,仿真得到的双边带噪声温度数值低于1000 K。在该前端基础上,完成了首次基于16QAM 数字调制体制的0.34 THz无线通信实验,传输速率达3 Gb/s。     

Low-noise millimeter- and submillimeter-wave receivers

A review of the current state in the development of receivers with an extremely low noise level in the short-wave part of the millimeter (mm) and submillimeter (submm)-wave bands is presented. A superheterodyne with a mixer at the input remains the main type of such receivers. The mixers using superconductor-insulator-superconductor (SIS) tunnel contacts and having noise temperatures very close to the quantum limit dominate at frequencies of up to ~1 THz. At the higher frequencies, the best results were obtained with hot-electron bolometers as mixers where the strong dependence of the semiconductor resistance on the temperature T_c is employed. Examples of the SIS receivers and cooled Schottky-barrier diode (SBD) receivers developed at the Institute of Applied Physics of the Russian Academy of Sciences are slightly inferior to SIS receivers in noise temperature but are useful for many applications. The prospects of low-noise reception in the mm and submm-wave bands, in particular the prospects of using integrated receivers and multipath systems, are discussed. Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 11, pp. 1424–1447, November, 1998.     

Device topological thermal management of β-Ga_2O_3 Schottky barrier diodes

The ultra-wide bandgap semiconductor β gallium oxide(β-Ga_2 O_3) gives promise to low conduction loss and high power for electronic devices. However, due to the natural poor thermal conductivity of β-Ga_2 O_3, their power devices suffer from serious self-heating effect. To overcome this problem, we emphasize on the effect of device structure on peak temperature in β-Ga_2 O_3 Schottky barrier diodes(SBDs) using TCAD simulation and experiment. The SBD topologies including crystal orientation of β-Ga_2 O_3, work function of Schottky metal, anode area, and thickness, were simulated in TCAD, showing that the thickness of β-Ga_2 O_3 plays a key role in reducing the peak temperature of diodes. Hence, we fabricated β-Ga_2 O_3 SBDs with three different thickness epitaxial layers and five different thickness substrates. The surface temperature of the diodes was measured using an infrared thermal imaging camera. The experimental results are consistent with the simulation results. Thus, our results provide a new thermal management strategy for high power β-Ga_2 O_3 diode.     

High Doping Density Schottky Diodes in the 3MM Wavelength Cryogenic Heterodyne Receiver

The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes. The measured equivalent noise temperature T_eq of the diodes is 109 K at 20 K, which is much higher than the T_eq of the low doping density (“cryogenic”) diodes. In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier. This is the lowest noise temperature ever reported for a Schottky diode mixer receiver. The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used.     

Determination of the laterally homogeneous barrier height of thermally annealed and unannealed Au/p-InP/Zn-Au Schottky barrier diodes

We have identically prepared Au/p-InP Schottky barrier diodes (SBDs). The diodes were annealed up to 400 °C thermally. The barrier height (BH) for the as-deposited Au/p-InP/Zn-Au SBDs from the current-voltage characteristics have varied from 0.58 to 0.72 eV, and ideality factor n from 1.14 to 1.47. The BH for the annealed SBDs from the current-voltage characteristics have varied from 0.76 to 0.82 eV, and ideality factor n from 1.17 to 1.39. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited SBDs. We have determined a lateral homogeneous BH value of 0.72 eV for the as-deposited Au/p-InP SBD from the experimental linear relationship between barrier heights and ideality factors, and a value of 0.85 eV for the annealed Au/p-InP SBD. The increase of 0.13 eV in the BH value by means of 400 °C annealing has been ascribed to the formation of the excess charges that electrically actives on the semiconductor surface.     

Measurements of the sideband conversion gain ratio of a millimeter-wave heterodyne sub-harmonic mixer using a fourier transform spectrometer

A Fourier transform spectrometer, based on a Martin-Puplett polarisation rotation interferometer and using broad-band blackbody noise sources, has been used to study the sideband response i.e., conversion gain, of a room temperature Schottky diode sub-harmonic mixer operating at 300 GHz. The technique enables the response of the mixer to be characterised and preferentially tuned to one sideband, thereby improving the rejection of unwanted spectral components which can be present in the mixer image sideband.     

Measured mixer noise temperature and conversion loss of a cryogenic Schottky diode mixer near 800 GHz

We accurately measured the noise temperature and conversion loss of a cryogenically cooled Schottky diode operating near 800 GHz, using the UCB/MPE Submillimeter Receiver at the James Clerk Maxwell Telescope. The receiver temperature was in the range of the best we now routinely measure, 3150 K (DSB). Without correcting for optical loss or IF mismatch, the raw measurements set upper limits ofT _M=2850 K andL _M=9.1 dB (DSB), constant over at least a 1 GHz IF band centered at 6.4 GHz with an LO frequency of 803 GHz. Correction for estimated optical coupling and mismatch effects yieldsT _M=1600 K andL _M=5.5 dB (DSB) for the mixer diode itself. These values indicate that our receiver noise temperature is dominated by the corner cube antenna's optical efficiency and by mixer noise, but not by conversion loss or IF mismatch. The small fractional IF bandwidth, measured mixer IF band flatness from 2 to 8 GHz, and similarly good receiver temperatures at other IF frequencies imply that these values are representative over a range of frequencies near 800 GHz.     

Investigation of a heterodyne receiver with open structure mixer at 324 GHz and 693 GHz

The performance of a submillimeter heterodyne receiver using an HCOOH laser local oscillator and an open structure mixer with a Schottky barrier diode has been optimized for 693 GHz. Working at room temperature a single sideband (SSB) system noise temperature of 7,300 K, a mixer noise temperature of 6,100 K and a conversion loss of 12 dB has been achieved. The same receiver system has been investigated at 324 GHz using an HCOOD laser local oscillator yielding a noise temperature of 3,100 K (SSB), a mixer noise temperature of 2,400 K (SSB) and a conversion loss of 10 dB (SSB). An acousto-optical spectrometer has also been constructed, with 1024 channels and a channel-bandwidth of 250 kHz. The system NEP per channel was 2.5×10^–17 W/Hz^1/2 at 324 GHz and 5.0×10^–17 W/Hz^1/2 at 693 GHz.     

静电放电对功率肖特基二极管I-V及低频噪声特性的影响

本文基于人体放电模型分别对肖特基势垒二极管的阴极和阳极进行同一电压脉冲下的多次放电, 利用热电子发射理论、1/f噪声的迁移率涨落模型和白噪声理论, 分别深入研究静电放电损伤对器件I-V和低频噪声的影响. 结果表明, 静电放电作用于肖特基二极管阴极时损伤更严重, 噪声参量变化率更大. 随着放电次数的增加, 正向特性无变化, 反向电流总体增大, 偶有减小; 而正向和反向 1/f噪声均增大. 鉴于噪声与应力条件下器件内部产生的缺陷与损伤有关, 且更敏感, 故可将低频噪声特性用作肖特基二极管的静电放电损伤灵敏表征工具.     

A Broad-Band Low-Noise Schottky Diode Full-Height Waveguide Mixer from 80 to 115 GHz

The RF matching problem in the input circuit of the mm-wavelength whisker contacted Schottky diode mixer is studied. The experimental results, obtained on the 3mm wavelength mixer mounts in the broad band of frequencies from 80 to 115 GHz are presented. It is shown that advantage in the receiver noise temperature may be realized by the use of a full-height instead of 1/4-reduced-height waveguide because of reduction loss in the mixer input circuit even beginning from the 3mm-wavelength. With a full-height waveguide mixer the double sideband (DSB) receiver noise temperature is 300 divided by 350K over the 85 to 110 GHz band. Input bandwidth of the fullheight waveguide mixer (cap delta f _S/f _SO greater than 30%) is equal to 1/2-and close to 1/4-reduced-height waveguide mixers.     

Model of Schottky-barrier diode low-frequency noise

A planar Schottky-barrier diode (SBD) is represented by two parallel-connected diodes that describe processes in the central region and in the leakage region. Independent fluctuations of the junction parameters and of the base resistances are sources of 1/F noise. The experimentally verified noise model developed on this basis explains the diversity of current and dependences of SBD noise observed in practice.St. Petersburg State Engineering University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 2, pp. 167–178, February, 1993.     

Series resistance calculation for the Metal-Insulator-Semiconductor Schottky barrier diodes

An accurate way of determining the series resistance R_s of Schottky Barrier Diodes (SBDs) with and without the interfacial oxide layer using forward current-voltage (I–V) characteristics is discussed both theoretically and experimentally by taking into account the applied voltage drop across the interfacial layerV _i. For the experimental discussion, the forward biasI–V characteristics of the SBDs with and without the oxide layer fabricated by LEC (the Liquid-Encapsulated Czochralski) GaAs were performed. The SBD without the oxide layer was fabricated to confirm a novel calculation method. For the theoretical discussion, an expression ofV _i was obtained by considering effects of the layer thickness and the interface state density parameters on forward biasI–V of the SBDs. The valueR _s of the SBD with interfacial oxide layer was seen to be larger than that of the SBD without the interfacial oxide layer due to contribution of this layer to the series resistance. According to the obtained theoretical formula, the value ofV _i for the SBD with the oxide layer was calculated and it was subtracted from the applied voltage values V and then the value ofR _s was recalculated. Thus, it has been shown that this new value ofR _s is in much closer agreement with that determined for the SBD without the oxide layer as predicted. Furthermore, the curves of the interface states energy distribution of each sample are determined. It was concluded that the shape of the density distribution curve and order of magnitude of the density of the interface states in the considered energy range are in close agreement with those obtained by others for Au/n-GaAs Schottky diodes by Schottky capacitance spectroscopy.     

High energy electron radiation effect on Ni and Ti/4H-SiCSchottky barrier diode at room temperature

This paper reports that Ni and Ti/4H-SiC Schottky barrier diodes (SBDs) were fabricated and irradiated with 1~MeV electrons up to a dose of 3.43×10¹⁴~e/cm². After radiation, the Schottky barrier height φ _B of the Ni/4H-SiC SBD increased from 1.20~eV to 1.21~eV, but decreased from 0.95~eV to 0.94~eV for the Ti/4H-SiC SBD. The degradation of φ _B could be explained by interface states of changed Schottky contacts. The on-state resistance R_S of both diodes increased with the dose, which can be ascribed to the radiation defects. The reverse current of the Ni/4H-SiC SBD slightly increased, but for the Ti/4H-SiC SBD it basically remained the same. At room temperature, φ _B of the diodes recovered completely after one week, and the R_S partly recovered.     

Semiconductor Detectors, Mixers, and Frequency Multipliers for the Terahertz Band

The state of the art in the development of semiconductor detectors, mixers, and frequency multipliers based on Schottky-barrier diodes (SBDs) and heterojunction structures for uncooled terahertz receivers is reviewed. The present status of this field features a transition from quasi-optical designs based on dot-matrix, whisker-contacted SBDs to the designs with hybrid-integrated and monolithic constructions on the planar SBD base, which are positioned in a waveguide mount. The high-level performance of these planar devices is achieved by partially or completely removing or changing semiconductor substrates and/or using membrane constructions incorporated in the waveguide.