【作者】 尤伟；

【导师】 刘正民；

【作者基本信息】 兰州大学 ， 粒子物理与原子核物理， 2008， 博士

【摘要】 宽带隙半导体材料——GaN，由于其优良的物理和化学性质，使其在短波区发光器件、极端条件（譬如辐射环境）器件等领域有着重要和广泛的应用潜力和良好的市场前景。故而，对于GaN材料掺杂研究成为目前半导体材料研究领域的热点之一。作为常用的器件处理工艺，离子注入是一种有效的掺杂方式。由于离子注入对GaN材料的光学和电学特性有着较大的影响，同时对于GaN的不同发光带的发光机理还没有明确统一的认识，所以本工作重点对离子注入GaN材料光学特性的影响进行了研究，并对离子注入GaN材料的电学特性的影响以及不同离子注入绝缘的应用前景进行了探讨。值得一提的是实验同时对离子共注GaN技术进行了初步的探讨。实验过程中采用的注入方法为单离子注入（Be、Mg、Al、Si）和双离子混合注入（Mg+Be、Mg+Si）。其中单离子的剂量分别为：10¹³、10¹⁴、10¹⁵、10¹⁶／cm²；双离子的注入剂量为：10¹³、10¹⁴、10¹⁵／cm²（Mg+Be）和10¹³、10¹⁴、10¹⁵、10¹⁶／cm²（Mg+Si），注入是在室温的条件下进行的。注入后的样品在950℃的流动氮气的环境下进行热退火，退火时间为30分钟。对退火前后的样品分别进行室温光致发光、拉曼散射光谱及霍尔效应的测量，通过对测量结果的分析得到了以下主要结论：1)通过对GaN光致发光特性的分析确定GaN材料的黄光发射起因于带隙间杂质能级间的跃迁，是典型的D_sA_dP跃迁，即浅施主向深受主的跃迁。Be离子注入GaN增强黄光发射是缺陷复合体V_GaBe_i贡献的结果，该复合体在GaN带隙中引入了深受主能级。2)根据实验是在n型GaN中实现的注入以及黄光带是D_sA_dP跃迁的前提下，分别得到了关于施主和受主注入产生黄光发射的缺陷的浓度随不同掺杂离子浓度的两个变化关系式4．6和4．10。3)Mg／Si离子共注的实验结果表明与注入Mg的GaN蓝光带相关的深能级仍然是深受主能级，蓝光发射也是浅施主向深受主的跃迁，浅施主是Mg间位Mgi，而深受主有两种可能，或者是能级位于价带之上0．43eV的某一未知的缺陷；或者就是空间上与其分离的紧邻氮空位V_N的替位Mg_Ga，即复合体Mg_GaV_N。共注实验结果表明施主Si与受主Mg共注GaN材料确实能够增加受主Mg的溶解性。4)对未注入GaN黄光发射负责的点缺陷（镓空位及缺陷复合体）也同样对红光发射负责，只是由于其被不同种类的扩展缺陷所影响从而对发光带的峰位产生了变化或者说能级发生了变化。5)离子注入GaN的拉曼光谱中的298cm^-1（R1）的散射峰是来自声学声子贡献的无序激活拉曼散射（DARS），667 cm^-1（R3）散射峰则是来自光学声子贡献的结果。360 cm^-1（R2）散射峰强度随注入离子的种类、剂量以及退火温度的变化而变化，它是简单缺陷譬如空位和间隙原子等贡献的结果而不是复杂缺陷，并且极有可能是氮空位相关的缺陷引起的。6)不同种类离子注入都会使GaN薄膜产生压应力，压应力的大小与注入离子的剂量的依赖并不明显；离子注入产生的缺陷譬如空位和间位等以及注入离子与要取代的GaN主晶格位置的Ga或N原子所具有的原子尺寸的差别都会影响应力的大小，实验结果显示前者在离子注入GaN的实验中起着决定性的作用。7)由于在注入过程中产生大量的点缺陷或简单的缺陷络合物，形成电子和空穴的深层陷阱，阻止电子和空穴的流动，从而造成电阻值随离子注入剂量的增加而升高。高剂量的受主注入能够产生高的阻抗，其在高温退火后依然存在，具有一定的实用价值。8)Be离子在低剂量(10¹³cm^-2)注入GaN后主要还是以间位施主Be_i的形式存在而不是替位。当注入剂量为10¹⁴cm^-2时，Si离子的注入存在严重的自补偿，形成的受主补偿了原来以及Si离子注入所增加的载流子，使得电阻值升高；更高剂量的Si离子的注入则会使得GaN的电阻值显著降低。更多还原

【Abstract】 Gallium Nitride （GaN） is promising wide bandgap material for fabricating high-efficiency light emitting devices in the short-wavelength regions and extremely using devices. It is expected to perform in the radiation environment of military and astronautic domains. In modern device technology, ion implantation is usually employed. In present dessertation, the influence of ion implantation on GaN optical and elctrical properties were investigated; implanted properties of different ions about GaN were also studied; meanwhile, the research on co-implantation effect of GaN in our experiments was started.In this article, Be、Mg、Al、Si ions are used to implant into GaN at room temperature and the fluence range from 10¹³-10¹⁶/cm², Mg+Be and Mg+Si are co-implanted into GaN at room temperature with respective fluence in the range of 10¹³-10¹⁵/cm² and 10¹³-10¹⁶/cm². All the implanted GaN samples were anneald at 950℃for 30 min in a flowing nitrogen environment. Photoluminescence, Raman and electrical properties of different ions implanted GaN were investigated and draw the conclusion as follows:1) The broad yellow luminescence （YL） band ranging from 480 to 700nm was produced by the transition between the energy levels of impurities or defects which was called a shallow donor to deep accepter pair （D_sA_dP） transition. In Be-implanted GaN sample, a different YL mechanism is involved that Be might be expected to form interstitial donors Be_i which is more effective than O_N to stabilize V_Ga and then form complexes V_GaBe_i. The V_GaBe_i can form deep acceptor energy level which is responsible for the YL.2) The theoretical model is developed to deduce the concentration of the defect causing the YL as a function of implanting concentration, are expressed by equation 4.6 and 4.10.3) Co-implantation of Mg and Si results show that for Mg-implanted GaN the blue luminescence （BL） is also a DAP transition, the shallow donor is produced by Mg_i, and the deep acceptor energy level is produced by the complex Mg_GaV_N or an unknown defect which generate deep acceptor state at about 0.43eV above the VB. Meanwhile, the results of co-implantation of Mg and Si support the practice of co-implantation enhance Mg implant activation.4) The experimental results also show that the defect complex such as V_Ga and/or V_Ga-complex is also responsible for the red luminescence （RL）; the influence of ion implantation on RL is larger than YL, it means the acceptor energy level responsible for RL is not easy affected by ion implantation.5) Additional Raman peak at 298cm^-1（R1） is attribute to disorder-activated Raman Scattering （DARS）, the 667 cm^-1（R3） probably arises from the optical-phonon branch at the zone boundary. The intensity of 360cm^-1 （R2） is dependent on species of implanted ions, fluence and annealing temperature, which is assigned to local vibration of simple defects such as vacancy and interstitial defects, most probable is V_N-related defects.6) The implantation of different ions result in compressive stress of GaN films, compressive stress is almost not dependent on ion fluence; hydrostatic strain is caused by the unit cell expansion/contraction due to: the implantation induced defects such as vacancies and interstitials, and the substitution of host atoms by the implants which have different size than the host lattice atoms, furthermore, the former plays a most crucial role.7) Ion implantation can induce a lots of point defects and simple defect complexes, then form deep traps which capture the electron and/or hole, and result in the increase of resistivity. Acceptor implantation with high fluence will increase resistivity that has practical value.8) When Be ion fluence is 10¹³cm^-2, Be is expected to form interstitial donors Be_i rather than any shallow acceptors.. When Si ion fluence is 10¹⁴cm^-2, self-compensation effects limit the electron density in Si-implanted GaN and induce the increasing resistivity, more fluence could decrease the resistivity.更多还原