VGF法半绝缘GaAs单晶EL2浓度优化研究

为了获得高电阻率及迁移率的半绝缘GaAs单晶材料,采用经高压及水平合成不同工艺制得的GaAs多晶料,进行垂直梯度凝固(VGF)法半绝缘GaAs单晶生长,测试和分析相应单晶片的EL2浓度、C浓度及电阻率、迁移率等性能参数,对比和分析了GaAs化学计量比的不同对单晶EL2浓度及电学参数的影响,经多炉次实验,确定出GaAs单晶电阻率>1×10⁸Ω·cm及迁移率>5×10³ cm²/(V·s)时C浓度及EL2浓度的合理范围,并据此结论,指导MBE外延用半绝缘GaAs单晶生长,保证了半绝缘GaAs单晶在满足高电阻率和迁移率的同时,具有较高的重复性和一致性。     

13N超高纯锗单晶的制备与性能研究

13N超高纯锗单晶是制作超高纯锗探测器的核心材料。本文通过还原法获得还原锗锭,再由水平区熔法提纯获得12N高纯锗多晶,最后由直拉法生长得到13N超高纯锗单晶。通过低温霍尔测试、位错密度检测、深能级瞬态谱(DLTS)测试对13N超高纯锗单晶性能进行分析。低温霍尔测试结果显示,晶体头部截面平均迁移率为4.515×10⁴ cm²·V^-1·s^-1,载流子浓度为1.176×10¹⁰ cm^-3,导电类型为p型,位错密度为2 256 cm^-2;尾部截面平均迁移率为4.620×10⁴ cm²·V^-1·s^-1,载流子浓度为1.007×10¹⁰ cm^-3,导电类型为p型,位错密度为2 589 cm^-2。晶体深能级杂质浓度为1.843×10⁹ cm^-3。以上结果...     

高质量硼掺杂单晶金刚石同质外延及电学性质研究

突破高质量、高效金刚石掺杂技术是实现高性能金刚石功率电子器件的前提。本文利用微波等离子体化学气相沉积(MPCVD)法,以三甲基硼为掺杂源,制备出表面粗糙度0.35 nm,XRD(004)摇摆曲线半峰全宽28.4 arcsec,拉曼光谱半峰全宽3.05 cm^-1的高质量硼掺杂单晶金刚石。通过改变气体组分中硼元素的含量,实现了10¹⁶~10²⁰ cm^-3的p型金刚石可控掺杂工艺。随后,研究了硼碳比、生长温度、甲烷浓度等工艺条件对p型金刚石电学特性的影响,结果表明:在硼碳比20×10^-6、生长温度1 100 ℃、甲烷浓度8%、腔压160 mbar(1 mbar=100 Pa)时p型金刚石迁移率达到207 cm²/(V·s)。通过加氧生长可以提升硼掺杂金刚石结晶质量,降低杂质散射。当氧气浓度为0.8%时,样品空穴迁移率提升至 614 cm²/(V·s)。     

Cs3Bi2I9晶体的生长及辐射探测性能

采用布里奇曼法成功制备出大尺寸(φ15 mm×50 mm)、高质量的全无机金属卤化物类钙钛矿Cs₃Bi₂I₉单晶。室温下,该晶体属于六方晶系,空间群为P6₃/mmc,密度为5.07 g/cm³,晶胞参数为a=b=0.840 nm,c=2.107 nm,熔点为632 ℃。采用粉末X射线衍射谱、紫外-可见-近红外漫反射光谱、I-V测试等表征该晶体的性质。制备Au/Cs₃Bi₂I₉/Au三明治型器件结构,采用飞行时间技术测试Cs₃Bi₂I₉晶体的载流子迁移率,得到Cs₃Bi₂I₉晶体的电子迁移率为4.33 cm²·V^-1·s^-1。根据Hecht单载流子方程拟合得到Cs₃Bi₂I₉晶体的载流子迁移率寿命积(μτ)为8.21×10^-5 cm²·V^-1,并且在500 V偏压下对α粒子的能量分辨率达到39%。     

红外LED用掺硅HB-GaAs单晶纵向载流子浓度分布研究

GaAs单晶作为一种重要的LED衬底材料在光电器件中应用十分广泛,但载流子浓度(C.C.)分布不均、杂质浓度过高等缺陷会严重影响相关器件的性能.为制备纵向载流子浓度分布均匀的掺硅HB-GaAs单晶,本文探讨了单晶生长过程中熔区长度对纵向载流子浓度分布的影响.以高纯GaAs多晶为原料,设定不同的拉晶温度曲线,采用窄熔区技术进行晶体生长研究,最终生长出C.C.值分布更均匀、位错密度低(EPD≤10 000 cm-2)的<111>向N型掺硅GaAs单晶.利用辉光放电质谱法(GDMS)和范德堡法霍尔效应测试对晶体进行了表征,单晶纯度达到5N且无硼杂质沾污.     

基于单根InAs纳米线场效应晶体管的制备及其电学性能研究

利用化学气相沉积法在Si衬底上生长合成了InAs纳米线,制备了基于InAs纳米线场效应晶体管并研究了电输运特性.对器件的阈值电压、亚阈值斜率、跨导、场效应迁移率以及载流子浓度等参数进行了计算和讨论.结果表明,InAs纳米线器件阈值电压约为-6.0 V,亚阈值斜率为180.86 mV/decade,跨导值达0.85 μS,最大开关比达108,场效应迁移率高达436.3 cm2/(V·s),载流子浓度达6.6×1017 cm-3.     

高温退火Cu(111)衬底上生长高质量厘米尺寸单晶石墨烯（英文）

二维(2D)石墨烯具有原子层厚度,在电子器件中展示出突破摩尔定律限制的巨大潜力。目前,化学气相沉积(CVD)是一种广泛应用于石墨烯生长的方法,满足低成本、大面积生产和易于控制层数的需求。然而,由于催化金属(例如Cu)衬底一般为多晶特性,导致CVD法生长的石墨烯晶体质量相对较差。为此,通过高温退火工艺制备了Cu (111)单晶衬底,使石墨烯的初始成核过程得到了很好的控制,从而实现了厘米尺寸的高质量单晶石墨烯的制备。根据二者的晶格匹配关系,Cu (111)衬底为石墨烯生长提供了唯一的成核取向,相邻石墨烯成核岛的边界能够缝合到一起。单晶石墨烯具有高电导率,相较于原始多晶Cu上生长的石墨烯(1 415.7Ω·sq^-1),其平均薄层电阻低至607.5Ω·sq^-1。高温退火能够清洁铜箔,从而获得表面粗糙度较低的洁净石墨烯。将石墨烯用于场效应晶体管(FET),器件的最大开关比为145.5,载流子迁移率为2.31×10³ cm²·V^-1·s^-1。基于以上结果,相信本工作中...     

InP纳米线场效应晶体管的制备及其电学性能的研究

利用化学气相沉积法在Si/SiO2衬底上生长出了InP纳米线,制备了基于InP纳米线的底栅场效应晶体管并研究了其电输运特性.对不同生长温度器件的阈值电压、亚阈值斜率、场效应迁移率以及载流子浓度等参数进行了计算和比较.结果表明,生长温度对InP纳米线的形貌影响较大.800℃生长温度的InP纳米线性能较好,该器件阈值电压约为-8.5V,亚阈值斜率为142.4 mV/decade,跨导为258.6 nS,开关比＞106,场效应迁移率高达177.8cm2/(V·s),载流子浓度达2.1×101s cm-3.     

介电层修饰并五苯/红荧烯双有源有机薄膜晶体管的制备与性能研究

在Si/SiO₂衬底上使用聚甲基丙烯酸甲酯(PMMA)制备器件介电层的修饰层,改善介电层界面质量并诱导有源层生长,从而提高有源层的结晶程度。通过真空蒸镀法生长并五苯/红荧烯双层结构有源层,制备有机薄膜晶体管(OTFT),并研究器件性能随红荧烯层厚度变化的情况。测试结果表明,修饰后的器件阈值电压为-3.55 V,电流开关比大于10⁵,迁移率达到0.0558 cm²/V·s,亚阈值摆幅为1.95 V/dec,器件总体性能得到改善。     

Te溶剂Bridgman法CdMnTe晶体核辐射探测器的制备和表征

碲锰镉(CdMnTe)作为性能优异的室温核辐射探测器材料,可用于环境监测和工业无损检测领域。本文中采用Te溶剂Bridgman法生长In掺杂Cd_0.9Mn_0.1Te晶体,制备成10 mm×10 mm×2 mm大小的室温单平面探测器,研究了该探测器对²⁴¹Am@59.5 keV γ射线源的能谱响应。通过表征红外透过率、电阻率以及探测器能谱响应等参数,综合评定了探测器用CdMnTe晶体的质量、电学和探测器性能。结果表明,晶片的红外透过率均在55%以上,最好可达到60%。采用湿法钝化,100 V偏压下的漏电流由钝化前的9.48 nA降为钝化后的7.90 nA,钝化后的电阻率为2.832×10¹⁰ Ω·cm。在-400 V反向偏压下,CdMnTe探测器对²⁴¹Am@59.5 keV γ射线源的能量分辨率在钝化前后分别为13.53%和12.51%,钝化后的电子迁移率寿命积为1.049×10^-3 cm²/V。研究了探测器的能量分辨率随电压的变化特性,当偏压≤400 V时,探测器的能量分辨率主要由载流子的收集效率决定,而当偏压>400 V时,能量分辨率由漏电流决定。本文研究结果表明,Te溶剂Bridgman法生长的CdMnTe晶体质量较好,电阻率和电子迁移率寿命积满足探测器制备需求。     

Er:Lu2 O3单晶的导模法生长及性能表征

本文以高纯Lu₂O₃、Er₂O₃为原料,使用自主设计、制造的自动等径导模炉,采用导模法(EFG)生长了φ25 mm×20 mm的7.82%(原子数分数)Er:Lu₂O₃单晶,分凝系数为0.92,并探索了退火条件。X射线衍射仪(XRD)结果为纯相,X射线荧光光谱仪(XRF)结果证明杂质含量较低。利用吸收光谱计算在972 nm及1 535 nm附近的吸收截面,分别为3.24×10^-21 cm²、8.43×10^-21 cm²,半峰全宽(FWHM)分别为28.22 nm、27.31 nm。热学性能测试结果表明,在30 ℃时热导率为13.28 W·m^-1·K^-1。利用扫描电子显微镜(SEM)对晶体表面微观形貌进行了表征。     

Structural and electrical properties of GaSb, AlGaSb and their heterostructures grown on GaAs by metalorganic chemical vapor deposition

A systematic study of structural and electrical properties of GaSb and AlGaSb grown on GaAs by metalorganic chemical vapor deposition is reported. In general, the results obtained from surface morphologies, X-ray linewidths and Hall properties are consistent with each other and indicate that the optimal growth conditions for GaSb are at 525°C around V/III = 1. A highest hole mobility of 652 cm²/V · s at RT (3208 cm²/V · s at 77 K) and a lowest concentration of 2.8 × 10¹⁶ cm⁻³ (1.2 × 10¹⁵ cm⁻³ at 77 K) were obtained for GaSb grown under this optimal condition. Compared to the GaSb growth, a smaller V/III ratio is needed for the AlGaSb growth to protect the surface morphology. When Al was incorporated into GaSb growth, mobility decreased and carrier concentration increased sharply. The AlGaSb grown at 600°C had a background concentration about one order of magnitude lower than the AlGaSb grown at 680°C. Room-temperature current-voltage characteristics of GaSb/Al_xGa_{1 − x}Sb/GaSb show a rectifying feature when Al composition x is higher than 0.3, suggesting a valence-band discontinuity at the AlGaSb/GaSb interface. A leakage current much higher than the value predicted by the thermionic emission theory is observed at 77 K, presumably due to a large number of dislocations generated by the huge lattice mismatch between GaSb and GaAs.     

Tin and tellurium doping of InAs using SnTe in molecular beam epitaxy (MBE)

Tin telluride (SnTe) was utilized as an n-type dopant in the MBE growth of InAs epitaxial layers on GaAs substrates. The highest carrier concentration obtained was 2.9 × 10¹⁹ cm^-3 and the carrier density could be varied over three orders of magnitude by changing the SnTe source temperature. The highest mobilities obtained were 16,900 and 23,300 cm²/V … s at 300 and 77 K, respectively, for carrier concentration of 5 × 10¹⁶ cm^-3. Both Sn and Te were incorporated in the layers as determined by secondary ion mass spectroscopy (SIMS) analysis and the total concentration of Sn and Te were the same as the carrier density in the layer.     

A novel technique to reduce the concentration of carbon in LEC gallium arsenide

An in-situ method has been developed to reduce the concentration of carbon in the liquid encapsulated growth of gallium arsenide. Sublimated As₂O₃ was bubbled through a GaAs melt to remove carbon via the production of CO₂. When a melt of known high starting carbon concentration ( 30 × 10¹⁴ atoms/cm³) was bubbled with As₂O₃, the subsequent crystal contained 4 × 10 ¹⁴ carbon atoms/cm³. This low carbon crystal was subsequently carbon doped and regrown, demonstrating the ability to return As₂O₃ treated GaAs to desired carbon concentrations and electrical properties.     

Se-doped AlGaAs grown on GaAs(111)A by molecular beam epitaxy

The electrical properties of Se-doped Al_0.3Ga_0.7As layers grown by molecular beam epitaxy (MBE) on GaAs(111)A substrates have been investigated by Hall-effect and deep level transient spectroscopy (DLTS) measurements. In Se-doped GaAs layers, the carrier concentration depends on the misorientation angle of the substrates; it decreases drastically on the exact (111)A surface due to the re-evaporation of Se atoms. By contrast, in Se-doped AlGaAs layers, the decrease is not observed even on exact oriented (111)A. This is caused by the suppression of the re-evaporation of Se atoms, by Se---Al bonds formed during the Se-doped AlGaAs growth. An AlGaAs/GaAs high electron mobility transistor (HEMT) structure has been grown. The Hall mobility of the sample on a (111)A 5° off substrate is 5.9×10⁴ cm²/V·s at 77 K. This result shows that using Se as the n-type dopant is effective in fabricating devices on GaAs(111)A.     

The growth and physics of ultra-high-mobility two-dimensional hole gas on (311)A GaAs surface

We report on the molecular beam epitaxy growth of modulation-doped GaAs-(Ga,Al)As heterostructures on the (311)A GaAs surface using silicon as the acceptor. Two-dimensional hole gases (2DHGs) with low-temperature hole mobility exceeding 1.2×10⁶ cm² V⁻¹ s⁻¹ with carrier concentrations as low as 0.8×10¹¹ cm⁻² have been obtained. This hole mobility is the highest ever observed at such low densities by any growth technique. We also report the first observation of persistent photoconductivity in a 2DHG. An analysis of the number density and temperature dependence of the mobility leads us to conclude that the mobility is limited by phonon scattering above 4 K and interface scattering at lower temperatures.     

Influence of cooling rate on the liquid-phase epitaxial growth of Zn3P2

We report the liquid-phase epitaxial growth of Zn₃P₂ on InP (1 0 0) substrates by conventional horizontal sliding boat system using 100% In solvent. Different cooling rates of 0.2–1.0 °C/min have been adopted and the influence of supercooling on the properties of the grown epilayers is analyzed. The crystal structure and quality of the grown epilayers have been studied by X-ray diffraction and high-resolution X-ray rocking measurements, which revealed a good lattice matching between the epilayers and the substrate. The supercooling-induced morphologies and composition of the epilayers were studied by scanning electron microscopy and energy dispersive X-ray analysis. The growth rate has been calculated and found that there exists a linear dependence between the growth rate and the cooling rate. Hall measurements showed that the grown layers are unintentionally doped p-type with a carrier mobility as high as 450 cm²/V s and a carrier concentration of 2.81×10¹⁸ cm⁻³ for the layers grown from 6 °C supercooled melt from the cooling rate of 0.4 °C/min.