本文選題：LMBE + GaMnN�。� 參考：《山東師范大學(xué)》2014年博士論文

【摘要】：隨著半導(dǎo)體技術(shù)的發(fā)展，半導(dǎo)體芯片中晶體管的特征尺寸從十幾年前的0.35μm縮小為目前最先進(jìn)的22nm，這使得芯片的集成度提高了成千上萬(wàn)倍，同時(shí)芯片中晶體管器件之間的絕緣層的厚度也在不斷地減小。進(jìn)一步發(fā)展下去，當(dāng)緣層的厚度減小到一定程度將會(huì)出現(xiàn)量子隧道效應(yīng)從而導(dǎo)致絕緣層失效，進(jìn)而會(huì)導(dǎo)致整個(gè)集成電路無(wú)法工作。此外，光刻工藝也是半導(dǎo)體技術(shù)發(fā)展的一個(gè)主要瓶頸�？傊雽�(dǎo)體芯片中晶體管的特征尺寸不可能無(wú)限減小，其發(fā)展空間已經(jīng)十分有限，要進(jìn)一步提高芯片的集成度和性能就必須尋找新的出路。 近年來(lái)發(fā)展起來(lái)的自旋電子學(xué)有望同時(shí)利用稀磁半導(dǎo)體（DMS）材料中電子的電荷和自旋兩個(gè)自由度，從而為芯片集成度的提高和電路性能的提升提供了廣闊的空間。在稀磁半導(dǎo)體中，由于磁性離子固有的磁矩與能帶中電子自旋之間存在耦合交換作用，從而導(dǎo)致了許多新奇的物理現(xiàn)象，例如磁致絕緣體-金屬轉(zhuǎn)變、反�；魻栃�(yīng)、束縛磁極化子、巨塞曼分裂、巨法拉第效應(yīng)和負(fù)磁阻效應(yīng)等。這些新奇的物理特性為一些新技術(shù)的發(fā)展提供了條件，使其在磁感應(yīng)器、高密度非易失性存儲(chǔ)器、光隔離器、半導(dǎo)體激光器和自旋量子計(jì)算機(jī)等領(lǐng)域有廣闊的應(yīng)用前景。因此，稀磁半導(dǎo)體材料受到了各國(guó)科學(xué)家的關(guān)注，成為近年來(lái)的研究熱點(diǎn)。要研制實(shí)用化的自旋電子器件就必須制備出能在室溫下具有鐵磁性并能與現(xiàn)有半導(dǎo)體器件制造工藝相兼容的新型稀磁半導(dǎo)體材料，這也是目前的研究重點(diǎn)。自從2000年Science雜志報(bào)道了以GaMnN為代表的GaN基稀磁半導(dǎo)體材料的居里溫度可能達(dá)到室溫以上，很多研究小組對(duì)GaN基稀磁半導(dǎo)體材料進(jìn)行了大量的研究并取得了一定的進(jìn)展。但是，由于所用的實(shí)驗(yàn)設(shè)備、生長(zhǎng)條件、處理工藝以及摻雜元素的種類和數(shù)量等條件都不盡相同，所以實(shí)驗(yàn)結(jié)果很分散。即使是同一種材料，不同研究小組報(bào)道的結(jié)果也有很大差異，甚至得出相反的結(jié)論。對(duì)稀磁半導(dǎo)體材料鐵磁性的起源問(wèn)題還存在爭(zhēng)議。 本文在多種實(shí)驗(yàn)條件下進(jìn)行了大量的研究，期望找到最佳實(shí)驗(yàn)條件制備出理想的GaMnN稀磁半導(dǎo)體材料。AlGaN材料也是GaN系列材料的一種，以GaN/AlGaN異質(zhì)節(jié)為基礎(chǔ)的高遷移率晶體管在超高頻、耐高溫和大功率器件領(lǐng)域有著很多潛在的應(yīng)用。本文研究了稀土金屬Tb摻雜的GaN和AlGaN材料的各種性質(zhì)，以及Cr和Sm共同摻雜的AlGaN材料，希望在提高居里溫度以及實(shí)現(xiàn)磁性可控方面有所突破。主要研究成果如下： 1.用LMBE方法在藍(lán)寶石襯底上成功制備了居里溫度高達(dá)340K的GaMnN稀磁半導(dǎo)體薄膜。N2壓強(qiáng)對(duì)薄膜的性質(zhì)有很大的影響，隨著N2壓強(qiáng)從7.0Pa減小到0.75Pa，薄膜的結(jié)晶質(zhì)量變好了，晶粒尺寸變大了，同時(shí)樣品的飽和磁化強(qiáng)度（Ms）也增強(qiáng)了。當(dāng)N2壓強(qiáng)進(jìn)一步減小到0.15Pa時(shí)，薄膜的結(jié)晶質(zhì)量變差了，晶粒尺寸變小了并伴隨著龜裂紋，同時(shí)樣品的Ms也減弱了。從我們的實(shí)驗(yàn)結(jié)果看，制備GaMnN稀磁半導(dǎo)體薄膜的最佳N2壓強(qiáng)為0.75Pa。在樣品生長(zhǎng)的過(guò)程中通過(guò)調(diào)節(jié)N2壓強(qiáng)，就可以生長(zhǎng)出具有特定磁性的GaMnN薄膜。 2.退火處理工藝對(duì)GaMnN薄膜的性質(zhì)有很重的影響。未經(jīng)過(guò)退火處理的樣品的結(jié)晶質(zhì)量很差屬于非晶GaMnN薄膜。隨著退火時(shí)間從5min增加到25min，樣品的結(jié)晶質(zhì)量逐漸提高。然而，過(guò)長(zhǎng)的退火時(shí)間又會(huì)導(dǎo)致樣品的結(jié)晶質(zhì)量變差，我們的實(shí)驗(yàn)結(jié)果表明，在1000℃下最佳退火時(shí)間為25min。我們制備的GaMnN薄膜樣品中Mn離子既有+2價(jià)也有+3價(jià)，而它們的比例也隨退火時(shí)間的變化而變化，這對(duì)磁性有很重要的影響�？梢酝ㄟ^(guò)控制退火時(shí)間使樣品具有較好的結(jié)晶質(zhì)量，同時(shí)具有特定的磁性。 3.離子注入過(guò)程會(huì)對(duì)晶格造成損傷，導(dǎo)致薄膜的結(jié)晶質(zhì)量變差。退火處理工藝可以部分地修復(fù)晶格的損傷，但與原生樣品相比晶格略有膨脹。GaN:Tb和AlGaN:Tb兩種樣品在室溫下都表現(xiàn)出了鐵磁性，這可以用束縛極化子（BMP）理論來(lái)解釋。與GaN:Tb相比，AlGaN:Tb樣品中的原子平均飽和磁矩?cái)?shù)值幾乎是GaN:Tb樣品中的兩倍，我們推斷AlGaN:Tb樣品中的Al原子會(huì)對(duì)整個(gè)樣品的總磁矩造成影響，這還需要進(jìn)一步研究論證。 4.在室溫下，，Cr和Sm共摻雜的AlGaN樣品呈現(xiàn)出鐵磁性并且存在巨磁矩效應(yīng)，特別是在900℃下退火處理的樣品的巨磁矩效應(yīng)更加明顯。巨磁矩效應(yīng)可能來(lái)源于兩個(gè)方面：一個(gè)是Cr3+離子和Sm3+離子之間3d-4f耦合，另一個(gè)是AlGaN晶格中的Cr3+-BMP和Sm3+-BMP之間的耦合，也可能兩者都有。我們的研究表明，可以通過(guò)調(diào)節(jié)在AlGaN薄膜中摻雜的Cr離子和Sm離子的數(shù)量以及比例來(lái)調(diào)節(jié)薄膜的磁性。
[Abstract]:With the development of semiconductor technology, the characteristic size of transistors in semiconductor chips has been reduced from 0.35 mu m to the most advanced 22nm at present. This makes the chip's integration increased thousands of times, and the thickness of the insulating layer between transistors in the chip is also decreasing. Further development, when the edge layer is thick. A certain degree will reduce to a certain extent, the quantum tunneling effect will lead to the failure of the insulating layer, which will lead to the failure of the entire integrated circuit. In addition, the lithography process is also a major bottleneck in the development of semiconductor technology. In a word, the characteristic size of transistors in semiconductor chips can not be reduced infinitely, and the development space has been very useful. In order to further improve the integration and performance of chips, we must find new ways.
In recent years, the development of spintronics is expected to make use of the two degrees of freedom of electron charge and spin in the thin magnetic semiconductor (DMS) material, which provides a broad space for the enhancement of the chip integration and the improvement of the circuit performance. In dilute magnetic semiconductors, the existence of the intrinsic magnetic moments of the magnetic separation and the electron spin in the energy band exists in the dilute magnetic semiconductor. Coupling exchange, resulting in many new physical phenomena, such as magnetic insulator metal transition, anomalous Holzer effect, bound magnetopolaron, giant Zeeman splitting, giant Faraday effect and negative magnetoresistance effect. These new physical properties provide conditions for the development of some new technologies to make it in magnetic sensors, high density and non easy. There is a wide range of applications in the fields of loss of memory, optical isolator, semiconductor laser and spin quantum computer. Therefore, thin magnetic semiconductor materials have attracted the attention of scientists from all countries and become a hot spot of research in recent years. To develop practical spin electronic devices, it is necessary to produce ferromagnetic and can be available at room temperature. New thin magnetic semiconductor materials, which are compatible with semiconductor manufacturing processes, are also the focus of current research. Since 2000, Science magazine reported that the Curie temperature of GaN based dilute magnetic semiconductors, represented by GaMnN, may reach room temperature. Many research teams have done a lot of research on GaN Based Diluted Magnetic Semiconductor Materials. Some progress has been made. However, as the experimental equipment, the growth conditions, the processing technology and the variety and quantity of the doped elements are different, the experimental results are very scattered. Even the same material, the results of the different research groups are very different, and even the opposite conclusion is reached. The issue of the origin of ferromagnetism is still controversial.
In this paper, a lot of studies have been carried out in various experimental conditions. It is expected to find the best experimental conditions to prepare the ideal GaMnN thin magnetic semiconductor material.AlGaN material as well as a kind of GaN series. The high mobility transistor based on GaN/AlGaN heterojunction has many potential applications in the field of UHF, high temperature and high power devices. The properties of GaN and AlGaN doped with rare earth metal Tb and the Co doped AlGaN materials of Cr and Sm are studied in this paper. It is hoped that there are some breakthroughs in improving the Curie temperature and magnetic controllability. The main research results are as follows:
1. the.N2 pressure of GaMnN thin magnetic semiconductor thin film with Curie temperature up to 340K was successfully prepared by LMBE method on the sapphire substrate. The properties of the thin film were greatly influenced by the.N2 pressure of the thin film. With the decrease of the N2 pressure from 7.0Pa to 0.75Pa, the crystalline quality of the film became better, the grain size became larger, and the saturation magnetization (Ms) of the sample was also enhanced. When N2 pressure was pressed. When the intensity is further reduced to 0.15Pa, the crystalline quality of the film becomes worse, the grain size becomes smaller and the tortoise crack is accompanied by the Ms. From our experimental results, the optimum N2 pressure of the preparation of GaMnN thin magnetic semiconductor thin film is that 0.75Pa. can grow by adjusting the N2 pressure in the process of sample growth. Magnetic GaMnN film.
2. annealing process has a very heavy effect on the properties of GaMnN films. The crystalline quality of the samples without annealing is very poor in the amorphous GaMnN film. As the annealing time increases from 5min to 25min, the crystal quality of the samples increases gradually. However, the long annealing time will lead to the deterioration of the crystal quality of the sample, our experimental knot. The results show that the optimum annealing time at 1000 C is 25min.. The Mn ions in the samples of GaMnN films have both +2 valence and +3 valence, and their proportion also varies with the change of annealing time, which has a very important influence on the magnetic properties.
The 3. ion implantation process can cause damage to the crystal lattice, resulting in the deterioration of the crystalline quality of the film. The annealing process can partially repair the damage of the lattice, but compared with the original sample, two samples of.GaN:Tb and AlGaN:Tb exhibit ferromagnetism at room temperature, which can be explained by the theory of bound polaron (BMP). And GaN:T Compared with B, the average atomic saturation magnetic moment in the AlGaN:Tb sample is almost two times that of the GaN:Tb sample. We infer that the Al atom in the AlGaN:Tb sample will affect the total magnetic moment of the whole sample, which needs further study.
4. at room temperature, the AlGaN samples Co doped by Cr and Sm present ferromagnetism and have giant magnetic moment effect, especially the giant magnetic moment effect of the samples annealed at 900 C. The giant magnetic moment effect may come from two aspects: one is the 3d-4f coupling between the Cr3+ ion and the Sm3+ ion, the other is Cr3+-BMP in the AlGaN lattice and the other is the Cr3+-BMP in the AlGaN lattice and the other is the Cr3+-BMP and the Cr3+-BMP in the AlGaN lattice. The coupling between Sm3+-BMP may also have both. Our study shows that the magnetic properties of the films can be adjusted by regulating the number and proportion of the Cr ions and Sm ions doped in the AlGaN film.
【學(xué)位授予單位】：山東師范大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：O484.1

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