氮极性Ⅲ族氮化物薄膜的MOCVD生长及其发光二极管研究

发布时间：2018-06-03 21:35

  本文选题：Ⅲ族氮化物 + N极性　； 参考：《吉林大学》2016年博士论文

【摘要】：Ⅲ族氮化物具有优异的光学与电学性质,现已经广泛应用于发光二极管(LEDs)、激光器、光电探测器和大功率电子器件中。通常金属极性Ⅲ族氮化物薄膜具有较高的晶体质量,而高质量的N极性Ⅲ族氮化物薄膜制备则比较困难,因此大部分器件的应用中都采用了金属极性Ⅲ族氮化物材料。然而,N极性Ⅲ族氮化物的潜力还没有被充分挖掘,在增强型晶体管、高度缩放晶体管、光子探测器、太阳电池、齐纳隧道二极管等器件的应用中,N极性结构将比金属极性结构更有优势,N极性的结构也有利于提高LEDs和LDs的性能,如提高载流子的注入效率、减小载流子的溢出以及增加In的组分等,这吸引了很多研究者的兴趣。本文在蓝宝石衬底上开展了N极性GaN、InGaN和InN薄膜的生长和特性研究,取得的主要成果如下：1.研究了衬底倾斜角、成核层厚度、高温GaN生长温度以及Will比对N极性GaN薄膜性质的影响。结果表明,当蓝宝石衬底的倾斜角从0.3°增加到0.8。时,N极性GaN的晶体质量、光学质量以及表面形貌得到了极大的改善,这主要得益于大倾斜角蓝宝石衬底增加了表面的台阶密度,同时减小了台阶之间的距离,这增加了Ga吸附原子接触到台阶和扭折位置的概率,有利于形成台阶流生长模式,从而提高了薄膜的晶体质量。成核层的厚度为20 nm时,GaN薄膜的螺位错与刃位错密度出现了极小值,即薄膜的晶体质量最好。而高温GaN的生长温度从1000℃增加到1080℃时,GaN薄膜的“黄带”发光显著降低,说明较高的生长温度有利于提高N极性GaN薄膜的光学质量。在1080℃条件下,当Will比为1500时,N极性GaN薄膜的晶体质量最优,其螺位错与刃位错密度分别为4.70×107cm-2和3.13×108cm-2,表面的均方根粗糙度(RMS)值为0.331nm,背景电子浓度和迁移率分别达到了2.35×1017/cm3和509 cm2/V·s,这些性能指标均与Ga极性GaN薄膜的性能相当。2.在N极性GaN模板上生长了N极性InGaN薄膜,研究了生长温度、Ⅴ/Ⅲ比、三甲基铟(TMIn)流量以及生长压力对N极性InGaN薄膜性质的影响。结果表明,较低的生长温度和大TMIn流量是增加薄膜的In组分的最有效的方法,但In组分的增加使InGaN与GaN之间的晶格失配增加,不可避免的降低了InGaN薄膜的晶体质量。较高的生长温度有利于提高N极性InGaN薄膜的晶体质量和光学质量,在760℃及以上的生长温度下,薄膜都有较强的近带边发光,而生长温度低于740℃时,近带边发光减弱,深能级发光逐渐占主导。由于In的平衡分压比Ga高很多,存在于气相中用以维持平衡的In占In的总输入量的比例较大,因而薄膜中的In组分对TMIn的输入量更为敏感。N极性InGaN薄膜的表面粗糙度随生长温度和压力的增加而降低。较高的生长压力有利于抑制In-N键的分解,在提高薄膜的晶体质量的同时也增加了薄膜中的In组分。3.制备了蓝紫光和蓝绿光的N极性LED。在样品的X射线衍射(XRD)2θ-ω扫描谱中可清晰地显示出高级卫星峰,说明N极性LED材料具有较好的晶体质量。器件的表面粗糙度较低,蓝紫光LED的表面RMS值为1.45 nm,蓝绿光LED的表面RMS值为1.75 nm。在200 mA的注入电流下,蓝紫光LED发光波长为411 nm,蓝绿光LED的发光波长为483 nm。4.在N极性GaN模板上生长了N极性InN薄膜,研究了生长温度、NH3流量、TMIn流量以及脉冲生长方法对N极性InN薄膜性质的影响。结果表明,与In极性InN薄膜相比,N极性InN表面较为平坦,而In极性InN表面被六方小丘覆盖。此外,N极性InN薄膜中存在着不同密度的In极性畴,我们认为In极性畴起源于下方GaN模板层的单晶畴边缘,在InN生长的初始阶段便形成了In极性晶核,随着生长的进行In极性晶核逐渐长大形成单晶畴。In极性畴密度随着生长温度或TMIn流量的增加而增加,且随NH3流量的减小而减少。这是由于GaN单晶畴边缘对表面吸附的In原子的迁移具有阻挡作用,不同生长条件下In表面吸附原子的迁移能力不同,因而迁移至GaN单晶畴边缘的几率不同,进而形成In极性InN晶核的密度不同。N极性InN在KOH溶液中的腐蚀速率高于In极性InN的腐蚀速率。XRD测试结果显示,相同生长条件下,N极性InN衍射峰位于31.3。,而In极性畴的衍射峰位于32.1。附近。此外,XRD极图测试中发现N极性InN薄膜中存在闪锌矿结构的InN,而且在闪锌矿InN的侧壁上还长有纤锌矿结构的InN这种复杂结构。随后在腐蚀后的SEM照片中我们发现了这种复杂结构,并且这种复杂结构具有1个上表面为N极性的闪锌矿InN内核和3个在侧壁上生长的In极性纤锌矿InN单晶畴。我们采用了脉冲生长法得到了晶体质量最好的N极性InN,其(0002)面摇摆曲线半峰宽为1.35。。
[Abstract]:III nitride has excellent optical and electrical properties and is now widely used in light-emitting diodes (LEDs), lasers, photodetectors and high-power electronic devices. Generally, metal polar III nitride films have high crystal quality, while high quality N polar III nitride films are difficult to prepare, so most of them are difficult to be prepared. Metal polarity III nitride materials have been used in the devices. However, the potential of N polar III nitride has not been fully exploited. In the applications of enhanced transistors, high scaling transistors, photon detectors, solar cells, Zener tunnel diodes, and other devices, the N polarity structure will be more advantageous than the metal polar structure, N pole. The sexual structure also helps to improve the performance of LEDs and LDs, such as increasing the carrier injection efficiency, reducing the overflow of the carrier and increasing the group of In, which attracts many researchers' interest. The growth and properties of N polar GaN, InGaN and InN films on sapphire substrate are studied in this paper. The main achievements are as follows: 1. The effects of substrate dip angle, nucleation layer thickness, high temperature GaN growth temperature and Will ratio on the properties of N polar GaN film show that when the inclination angle of the sapphire substrate increases from 0.3 to 0.8., the crystal quality, optical quality and surface morphology of N polar GaN are greatly improved, mainly due to the large inclined sapphire substrate. The step density of the surface is increased and the distance between the steps is reduced, which increases the probability that the Ga adsorbed atoms contact the step and the torsional position, which is beneficial to the formation of the step flow growth mode and thus improve the crystal quality of the film. When the thickness of the nucleation layer is 20 nm, the snail dislocation and the edge dislocation density of the thin film of GaN have a minimum value, that is, The crystal quality of the thin film is the best. While the growth temperature of the high temperature GaN is increased from 1000 to 1080, the "yellow band" luminescence of the GaN film is significantly reduced. It shows that the higher growth temperature is beneficial to the improvement of the optical quality of the N polar GaN film. At the temperature of 1080, the crystal quality of the N polar GaN film is the best when the Will ratio is 1500, and its screw dislocation and edge is the blade. The dislocation density is 4.70 x 107cm-2 and 3.13 x 108cm-2 respectively. The surface RMS roughness (RMS) value is 0.331nm, and the background electron concentration and mobility reach 2.35 * 1017/cm3 and 509 cm2/V s respectively. These performance indexes are equal to Ga polarity GaN thin films, and.2. on N polar GaN template has grown on the polar polarity GaN template and studied the growth temperature. Degree, V / III ratio, the effect of TMIn flow and growth pressure on the properties of N polar InGaN films. The results show that the lower growth temperature and the large TMIn flow are the most effective methods to increase the In component of the thin film, but the increase of the In component increases the lattice mismatch between InGaN and GaN, and inevitably reduces the crystal of the InGaN thin film. The high growth temperature can improve the crystal quality and optical quality of the N polar InGaN film. At the growth temperature of 760 C and above, the thin film has a strong near band edge luminescence. While the growth temperature is lower than 740, the near band edge luminescence is weakened and the deep level luminescence gradually dominates. The equilibrium partial pressure of In is much higher than that of Ga. The proportion of In used in the gas phase to maintain the balance of the total input of In is larger, so the In component in the film is more sensitive to the input of TMIn. The surface roughness of the.N polarity InGaN film decreases with the increase of growth temperature and pressure. The higher growth pressure is beneficial to the inhibition of the decomposition of the In-N bond, while improving the crystal quality of the thin film. The N polarity LED. of blue violet light and blue and green light in the In component.3. in the film is also increased. The high satellite peak can be clearly displayed in the sample's X ray diffraction (XRD) 2 [theta] Omega scanning spectrum. It shows that the N polarity LED material has better crystal quality. The surface roughness of the device is lower, the RMS value of the blue violet LED is 1.45 nm, and the blue and green light LED. With the surface RMS value of 1.75 nm. at the injection current of 200 mA, the luminescence wavelength of blue violet LED is 411 nm, the luminescence wavelength of blue and green LED is 483 nm.4., and N polarity InN film is grown on N polar GaN template. The effect of growth temperature, NH3 flow, flow rate and pulse growth method on the properties of polar membrane are studied. Compared with the N film, the surface of the N polar InN is relatively flat, while the In polar InN surface is covered by six square hills. In addition, there are different densities of In polarity domains in the N polar InN film. We think the In polarity domain originates from the single crystal domain edge of the lower GaN template layer below, and the In polar crystal nucleus is formed at the initial stage of InN growth. The crystal nucleus gradually grows up to form a single crystal domain.In polarity domain density increases with the increase of growth temperature or TMIn flow, and decreases with the decrease of NH3 flow. This is due to the barrier effect of the migration of In atoms adsorbed on the surface of GaN single crystal, and the migration ability of the adsorbed atoms on the surface of In is different under different growth conditions and thus migrates to Ga. The probability of the domain edge of the N single crystal is different, and then the density of the In polarity InN nucleus is formed. The corrosion rate of the.N polar InN in KOH solution is higher than that of the In polar InN, and the results show that the InN diffraction peak of N polarity is located in the 31.3., and the diffraction peak of the polarity domain is located near the same growth condition. The present N polar InN film has a InN of sphalerite structure and the complex structure of the zinite structure on the side wall of the sphalerite InN. This complex structure has been found in the SEM photos after corrosion, and this complex structure has 1 sphalerite InN kernel on the surface of N polarity and 3 growth on the side wall. The In polar wurtzite InN single crystal domain is obtained. The N polar InN with the best crystal quality is obtained by pulse growth method, and its (0002) rocking curve half peak width is 1.35..
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN312.8

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1 陆大成,段树坤;A Quasi-Therm odynam ic Model of MOVPE of InGaN[J];半导体学报;2000年02期

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