太赫兹半导体探测器、发射器和功率放大器的制备及性能研究

发布时间：2018-06-19 04:43

本文选题：太赫兹半导体器件 + 自开关二极管　；参考：《山东大学》2017年博士论文

【摘要】：太赫兹波是指频率为0.1～10 THz(1 THz = 1000 GHz)的电磁波辐射,其频率介于微波和红外之间。由于以前产生和探测太赫兹频率的电磁辐射无论在电子学还是在光学领域中都有非常大的困难,导致人们对这个频段的电磁波的性质认识和应用都非常少,所以太赫兹频段又常被称为"太赫兹空隙"(THz gap)。最近十几年,随着被发现在国防、超高速无线通信、物相分析、宇宙光谱学和安检成像等领域有非常重要的潜在应用,太赫兹波迅速得到了大家的广泛重视。一直以来严重阻碍人们对于太赫兹波的研究和应用的最大问题是缺乏合适的太赫兹源和探测器。目前已有的太赫兹设备或器件大多存在体积庞大、造价昂贵、需要极低的工作温度等问题,无法大规模应用。近年来,得益于微电子领域半导体材料的生长技术和微纳加工工艺的飞速发展,利用高速半导体器件实现太赫兹的发射和探测已经成为可能。半导体太赫兹器件具有成本低、体积小、功耗低、效率高、可集成等诸多优势,因而高性能半导体太赫兹器件的研制被大家公认为是未来能够推动太赫兹技术发展与应用的重要动力。本论文针对目前国内外太赫兹半导体器件研究、发展的现状,以新型平面半导体器件为主要研究方向,利用微纳加工技术,成功制备了太赫兹平面半导体探测器、发射器和功率放大器,并系统的研究了器件的工作原理、直流和高频特性以及对器件性能优化提升的方法。主要研究内容如下:1)制备了高性能太赫兹平面半导体探测器-自开关二极管(SSD),并研究了提高其响应度的方法。在高迁移率半导体材料上制备的SSD由于寄生电容小,工作频率最高可达1.5 THz,但是器件响应度不高。本论文研究了通过在SSD沟槽中填充电介质材料的方法提高SSD响应度,并对比了 PMMA和Si0_2两种介质材料对器件直流和高频性能的影响。实验结果发现在用PMMA填充SSD沟槽后,器件直流I-V曲线中的开关比显著提高、器件的线性度明显改善、器件的高频响应度有大幅度提升,测得的最高响应度达到1650mV/mW,比未填充PMMA的SSD提高了一个数量级。2)研究了利用干法刻蚀制备SSD的工艺以及刻蚀掩膜对器件性能的影响。首次提出了使用无损伤的热蒸发法沉积的一氧化硅(SiO)做刻蚀掩膜来提高器件高频性能的方法。SSD的整流特性依赖于宽度只有几十纳米的沟道和沟槽。之前器件制备时主要利用湿法工艺刻蚀沟槽,因此存在重复性差,边缘粗糙,侧壁不垂直等问题。虽然也有利用干法刻蚀制备SSD的报道,但器件性能普遍不佳。本论文中通过分析发现刻蚀掩膜对于干法刻蚀制备的SSD的性能有明显的影响。在对比研究旋涂法制备的有机光刻胶掩膜和等离子体方法沉积的无机掩膜所存在的问题后,我们首次提出了用热蒸发的SiO做微纳加工的干法刻蚀掩膜。热蒸发的SiO晶粒小、平整度好,耐刻蚀能力强,非常适合做刻蚀掩膜材料。更重要的是和其它无机掩膜采用的溅射或等离子体增强化学气相沉积(PECVD)等方法比,SiO的热蒸发沉积方式不会对半导体材料表面造成损伤。因此使用热蒸发的SiO做刻蚀掩膜可以显著提高载流子靠近表面(如二维电子气)的半导体器件的性能。实验中通过与旋涂的PMMA和溅射的Si0_2做对比,发现利用热蒸发的SiO刻蚀掩膜制备的SSD不但刻蚀图形形貌良好,器件的高频性能也有明显的提高。用SiO掩膜制备的器件在220 GHz的频率下的响应度比用另外两种掩膜制备的器件的响应度高1到2个量级,等效噪音功率低超过1个量级。通过对制备的Hallbar做霍尔测试,发现用SiO掩膜刻蚀的沟道中的载流子的浓度和迁移率都高于用溅射Si0_2掩膜刻蚀的沟道,尤其是载流子迁移率高了一倍。这充分说明了热蒸发法沉积的SiO在提升高频微纳器件性能方面具有明显的帮助作用。3)研究了 InGaAs SSD表面氧化层的处理对沟道表面耗尽区宽度和费米能级钉扎效应的影响。InGaAs材料由于表面氧化等原因,存在大量的表面态,这些表面态对纳米宽度的SSD沟道有直接的影响。本论文通过测试SSD的电导率与沟道宽度的关系,得出了 SSD表面耗尽区宽度为46 nm。进一步研究发现用酸去除表面氧化层后表面耗尽区宽度会增加至74 nm,而用氧等离子体对表面进行氧化处理后耗尽区宽度则会降低至35 nm。这说明InGaAs材料表面耗尽层宽度会随半导体表面状态的改变而发生明显变化,分析发现这种变化与表面态密度的改变以及费米能级钉扎位置的移动有关。4)研究了 GaN纳米器件的加工工艺,并成功制备了基于GaN SSD的太赫兹探测器。GaN材料作为新一代宽禁带半导体的代表,具有耐高温、耐击穿、耐辐射等优点,在太空、军事等领域都有巨大的应用前景。SSD具有结构简单、工作频率高的特点。将两者结合可以充分发挥其各自的优势。本论文研究了 GaN SSD的制备工艺和器件性能。利用热蒸发的SiO做掩膜的干法刻蚀工艺实现了宽度仅30 nm,深度达135 nm的SSD沟槽,而且刻蚀边缘清晰平直,底部平整。GaN SSD的高频测试结果证实其工作频率超过220 GHz,而且具有良好的线性响应度,证明GaNSSD可以作为太赫兹探测器。本论文同时也对GaN SSD未来在器件性能优化方面的研究方向做了论述。5)设计和制备了基于平面耿氏二极管(PGD)的高频大功率太赫兹源,并提出了一种基于共平面波导(CPW)的二维谐振腔。半导体异质结PGD是近十年才被发现其优势特点并开始研究的。目前报道的器件基频工作频率已超过300GHz,远超传统垂直耿氏二极管,有望在未来成为广泛应用的太赫兹半导体发射器。但是目前PGD的发射功率仍然偏低。本论文通过研究优化半导体异质结衬底结构以及器件的结构和制备工艺,大幅度提升了器件的微分负阻效应。器件在微分负阻区电流峰谷比达到1.25,超过了文献报道的最高值。同时借助于三维电磁场仿真,在本论文中提出了一种基于CPW的二维谐振腔。将其于PGD上后,成功制备出发射频率超过100 GHz,发射功率远超文献报道,达到0.8mW的太赫兹发射源。这是首次将PGD的发射功率提高到毫瓦量级。另外发射器的相噪音和频率的稳定性等指标也得到了明显的提升。测得的相噪音只有-107 dBc/Hz,比文献报道的同类型器件低30 dB。发射频率随直流偏压的漂移只有0.21GHz/V,达到领先水平。6)探究了 GaN PGD的器件制备工艺并讨论了 GaN耿氏二极管存在问题和未来的发展方向。GaN材料由于带隙宽、耐高温、耐击穿,载流子饱和漂移速率高,非常适合用于制备高频大功率耿氏器件。本论文探究了 GaN PGD的制备工艺。制备的GaN PGD在电场强度达到7 V/μm后,电流随电压增长速度开始明显放慢,表现出一定程度的饱和现象。GaN基太赫兹源的研制是世界难题,本论文针对GaN PGD存在的问题做了一些研究,并对未来的相关研究提出了建议。7)首次提出利用平面耿氏器件做太赫兹功率放大器,成功制备了工作频率超过110GHz的平面功率放大器,并系统研究了放大器的各项性能。太赫兹系统离不开功率放大器,基于高迁移率场效应晶体管(HEMT)的功率放大器虽然目前截止频率已经达到0.6 THz,但是要求器件沟道长度缩短至25 nm左右以降低RC时间和电子渡越时间。如此严苛的要求使得器件的制备变的极其困难,也因此器件价格非常昂贵,难以大规模应用。其它的功率放大器,包括异质结双极性晶体管(HBT)、共振隧穿二极管(RTD)等都存在大功率情况下线性度差,信号失真的问题。本论文中首次提出了一种新型太赫兹功率放大器-平面耿氏放大器。它利用耿氏器件的微分负阻效应实现太赫兹功率放大。通过改进器件结构及工艺,提高了器件的微分负阻效应,在InGaAs衬底上制备的平面耿氏放大器增益达到17 dB,截止频率超过110 GHz。而且器件功率特性良好,1 dB压缩点为0 dBm,远超HBT和RTD。研究还发现平面耿氏放大器的最佳工作频率与沟道长度成反比,沟道长度为300nm的器件的工作频率可达0.6THz,这比具有相同频率的HEMT器件的沟道长度大10倍左右。大的沟道尺寸可以明显降低器件制备的难度,从而大幅度降低器件的成本。另外对平面耿氏放大器具有功率密度低、散热好的优势,因此工作稳定性也更好。实验中在没有对器件采取衬底减薄和加装散热片等垂直耿氏器件必须使用的降温措施的情况下,器件连续工作2小时仍然保持功率增益为16 dB,波动小于0.8 dB。8)制备二维侧栅晶体管(SGT)并对器件的工作机理、等效电路、直流转移和输出特性等做了研究。SGT在结构和工作机理上与SSD有非常大的相似性。通过对SGT的研究可以获得如阈值电压、开关比、载流子迁移率、缺陷态密度、沟道电容等一些仅仅通过对SSD的测量和分析很难获得的参数,而且利用SGT可以有针对性的研究这些参数与器件结构、制备工艺等的关系,这对于提高SSD的性能有重要的指导意义。本论文中成功制备了沟道宽度为90～150nm的SGT,测得沟道宽度为135 nm的SGT的阈值电压为-0.8 V,器件的最佳工作点为0.5 V,最大跨导为24.1 μS。
[Abstract]:The terahertz wave refers to the electromagnetic wave radiation of 0.1 ~ 10 THz (1 THz = 1000 GHz). Its frequency is between microwave and infrared. Since the electromagnetic radiation produced and detected in the terahertz frequency is very difficult both in electronics and in the optical field, people understand the properties of the electromagnetic wave in this band. Terahertz (THz gap) is often called terahertz (terahertz). In the last decade, there are very important potential applications in the fields of national defense, ultra high speed wireless communication, phase analysis, cosmic spectroscopy and security imaging. The terahertz wave has been widely paid attention to. It has been seriously hindered. The biggest problem for the research and application of the terahertz wave is the lack of appropriate terahertz sources and detectors. Most of the existing terahertz devices or devices exist in large volume, expensive and very low working temperature. In recent years, the growth technology of semiconductor materials in microelectronics has been benefited. With the rapid development of operation and micro nano processing technology, it is possible to realize the emission and detection of terahertz by high-speed semiconductor devices. The semiconductor terahertz device has many advantages, such as low cost, small volume, low power consumption, high efficiency, and can be integrated. The development and application of terahertz technology is important. In this paper, the development of terahertz semiconductor devices at home and abroad is the main research direction. Using the new type of planar semiconductor devices as the main research direction, the terahertz semiconductor detector, emitter and power amplifier are successfully prepared by using micro nano technology. The principle of the device, the characteristics of DC and high frequency and the optimization of the performance of the device. The main research contents are as follows: 1) the high performance terahertz planar semiconductor detector - self switched diode (SSD) is prepared and the method to improve the response degree is studied. The SSD of the high transfer rate semiconductor material is small because of the small parasitic capacitance. The working frequency is up to 1.5 THz, but the response degree of the device is not high. In this paper, the response degree of the SSD is improved by filling the charging medium in the SSD groove, and the influence of the two dielectric materials on the DC and high frequency performance of the devices is compared. The experimental results show that the DC I-V curve of the device after filling the SSD groove with PMMA is found. The switch ratio of the device is greatly improved, the linearity of the device is obviously improved, the high frequency response degree of the device is greatly improved, the maximum response of the device is up to 1650mV/mW, and an order of magnitude.2 is higher than that of the unfilled PMMA SSD. The process of using dry etching to prepare the SSD and the effect of the etching mask on the performance of the device are studied. The method of using SiO to improve the high frequency performance of the device is to improve the high frequency performance of the device. The rectification characteristic of.SSD depends on the channel and groove with a width of only a few tens of nanometers. However, there are also reports of the use of dry etching to prepare SSD, but the performance of the devices is generally poor. In this paper, it is found that the etching mask has an obvious effect on the performance of SSD prepared by dry etching. After comparing the problems of organic photoresist mask prepared by spin coating and the problems of the plasma method deposited inorganic masks, we have found that A dry etching mask with heat evaporated SiO for micro nano processing is proposed for the first time. The heat evaporated SiO has small grain, good evenness, strong corrosion resistance, and is very suitable for etching masks. More importantly, the ratio of sputtering or plasma enhanced chemical vapor deposition (PECVD) to other inorganic masks, and the thermal evaporation deposition of SiO There is no damage to the surface of the semiconductor material. Therefore, the performance of a semiconductor device with a carrier near the surface (such as two-dimensional electron gas) can be significantly improved by using a thermal evaporated SiO as an etching mask. In the experiment, the SSD produced by the SiO etching mask using the hot steamed SiO is not only etched by comparison with the Si0_2 of the spin coating and sputtering. The high frequency performance of the device is obviously improved. The response degree of the device prepared by the SiO mask at 220 GHz is 1 to 2 orders of magnitude higher than that of the other two kinds of masks, and the equivalent noise power is lower than 1 orders of order. The Holzer test of the prepared Hallbar is used to find the channel etching channel with the SiO mask. The concentration and mobility of the carrier is higher than that of the channel etched by the sputtering Si0_2 mask, especially the mobility of the carrier. This shows that the SiO deposited by thermal evaporation has a significant help in improving the performance of the high frequency micro devices. The treatment of the surface depletion of the InGaAs SSD surface to the channel surface depletion has been studied. The effect of zone width and Fermi energy level pinning effect on.InGaAs material has a large number of surface states due to surface oxidation. These surface states have a direct influence on the SSD channel of nanoscale width. This paper has found that the width of the SSD surface depletion region is 46 nm. by testing the relationship between the conductivity of the SSD and the channel width. The width of the surface depletion region will increase to 74 nm after the surface oxidation layer is removed with acid, and the depletion region width will decrease to 35 nm. after the oxidation treatment of the surface with oxygen plasma. It shows that the width of the surface depletion layer of the InGaAs material will change obviously with the change of the surface state of the semiconductor, and the analysis shows that the change and the surface density of the surface are found. The processing technology of GaN nano devices is studied by the change of.4 and the movement of Fermi level pinning position. The.GaN material of the terahertz detector based on GaN SSD is successfully prepared as the representative of a new generation wide band gap semiconductor, which has high temperature resistance, breakdown resistance, radiation resistance and so on. It has great application in space, military and other fields. .SSD has the characteristics of simple structure and high working frequency. Combining the two can give full play to their respective advantages. This paper studies the preparation technology and device performance of GaN SSD. The dry etching process of the mask by thermal evaporation of SiO has realized a SSD groove with a width of only 30 nm and a depth of 135 nm, and the etching edge is clear and flat. Bottom of the etching is clear and flat. The high frequency test results of the flat.GaN SSD confirm that the working frequency is more than 220 GHz, and has a good linear response degree, which proves that GaNSSD can be used as a terahertz detector. This paper also discusses the direction of GaN SSD in the future research direction of the device performance optimization, and sets up and prepared the planar Gunn diode (PGD). High frequency and high power terahertz source, a two-dimensional resonant cavity based on common plane waveguide (CPW) is proposed. Semiconductor heterojunction PGD is discovered in recent ten years and has been discovered. The frequency of basic frequency of devices is over 300GHz, far beyond the traditional vertical Gunn diode, which is expected to be widely used in the future. The transmission power of PGD is still low. In this paper, the differential negative resistance effect of the device is greatly improved by optimizing the structure of the semiconductor heterojunction substrate and the structure and fabrication process of the device. The current peak to valley ratio of the differential negative resistance region is up to 1.25, which exceeds the highest value reported in the literature. With the aid of three-dimensional electromagnetic simulation, a two-dimensional resonant cavity based on CPW is proposed in this paper. After it is on PGD, the emission frequency is more than 100 GHz and the emission power is far beyond the literature to reach the terahertz emission source of 0.8mW. This is the first time that the emission power of PGD is raised to milliwatts. And the phase noise of the emitter and the phase noise of the emitter. The frequency stability and other indexes have been improved obviously. The measured phase noise is only -107 dBc/Hz, which is 30 dB. lower than the same type device reported in the literature. It is only 0.21GHz/V to reach the leading level of.6.) the preparation process of GaN PGD is explored and the existence of GaN Gunn diode is discussed and the future is discussed. Due to the wide band gap, high temperature resistance, breakdown resistance and high carrier saturation drift rate, the development direction.GaN is very suitable for the preparation of high frequency high power Gunn devices. This paper explores the preparation process of GaN PGD. After the electric field strength reaches 7 V/ mu m, the current of the prepared GaN begins to slow down obviously with the growth rate of the voltage, showing a certain degree. The development of the.GaN based terahertz source is a world problem. This paper has done some research on the existing problems of GaN PGD, and proposed a suggestion.7 for the related research in the future. It is the first time that a plane Geng device is used as a terahertz power amplifier, and a planar power amplifier with a working frequency exceeding 110GHz has been successfully prepared and the system has been successfully prepared. The performance of the amplifier is studied. The terahertz system can not be separated from the power amplifier. The power amplifier based on the high mobility field effect transistor (HEMT) has the current cut-off frequency of 0.6 THz, but the channel length of the device is shortened to about 25 nm to reduce the time of RC and the time of electron crossing. The preparation of parts is extremely difficult, so the device is very expensive and difficult to be applied in large scale. Other power amplifiers, including heterojunction bipolar transistors (HBT), resonant tunneling diode (RTD), etc., have the problem of low linearity and signal distortion under high power conditions. In this paper, a new type of terahertz power amplifier is proposed for the first time. It uses the differential negative resistance effect of the Gunn device to achieve the terahertz power amplification. The differential negative resistance effect of the device is improved by improving the device structure and process. The gain of the planar Gunn amplifier on the InGaAs substrate is 17 dB, the cut-off frequency is over 110 GHz. and the power characteristic of the device is good, 1 dB The compression point is 0 dBm. The far super HBT and RTD. studies also find that the optimal operating frequency of the planar Gunn amplifier is inversely proportional to the channel length, and the operating frequency of the channel length of 300nm can reach 0.6THz, which is about 10 times larger than the channel length of the HEMT device with the same frequency. The large channel size can significantly reduce the difficulty of the device preparation. Furthermore, the cost of the device is greatly reduced. In addition, the plane Gunn amplifier has the advantages of low power density and good heat dissipation, so the work stability is better. In the experiment, in the case of the cooling measures must be used for the vertical Gunn device, such as the substrate thinning and the installation of the radiator, the device still works for 2 hours. With a power gain of 16 dB and a fluctuation less than 0.8 dB.8) a two-dimensional grid transistor (SGT) is prepared and the working mechanism, equivalent circuit, DC transfer and output characteristics of the device are studied. The structure and working mechanism of.SGT are very similar to that of SSD. By the study of SGT, the threshold voltage, the switch ratio, the carrier mobility can be obtained. Some parameters such as defect density, channel capacitance, etc. are difficult to obtain through the measurement and analysis of SSD, and the relationship between these parameters and device structure and preparation process can be studied by SGT, which is of great significance for improving the performance of SSD. In this paper, the channel width of 90 to 150nm is successfully prepared in this paper. GT, the threshold voltage of SGT with a channel width of 135 nm is -0.8 V, the optimum operating point of the device is 0.5 V, and the maximum transconductance is 24.1 S..
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN303

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