【作者】 李娟；

【导师】 王宇钢；

【作者基本信息】 北京大学 ， 核技术及应用， 2008， 硕士

【摘要】 GaN作为第三代半导体材料,因其优良的特性,日益成为研究的热点。它在微电子和光电子领域具有十分广阔的应用优势和发展前景,同时离子束辐照在加工这些器件方面具有很多优势,但是离子束辐照过程中产生的晶格损伤是不可忽略的,这些损伤往往对器件性能有害。本论文主要研究了低能重离子辐照GaN产生的晶格损伤,结合X射线衍射,沟道-背散射,原子力显微镜,扫描电子显微镜等手段表征被辐照GaN样品中的晶格损伤及表面形态。实验发现500keV的Au⁺离子束辐照GaN的剂量大于等于5×10¹⁴/cm²时,辐照区域出现肿胀,并且随着剂量的增加肿胀高度升高;不同退火温度下辐照区域出现不同程度的挥发。1000℃退火时辐照区由于挥发下降高度接近500keV的Au在GaN中的射程。另外,在研究中还发现剂量为1×10⁹-5×10¹⁵/cm²的低能Au⁺离子辐照GaN之后,GaN能被80℃的AZ-400K光刻胶显影液（有效成份为KOH）或者氢氧化钾溶液腐蚀,采用这种方法,统计腐蚀坑的数目为:10⁶/cm²-10⁸/cm²,远远低于离子束辐照剂量,但却与GaN的本征缺陷数目在同一个数量级。由此提出低剂量离子辐照后的GaN经过腐蚀其腐蚀坑的数目能反映GaN的本征缺陷数目。实验中还发现,不同剂量下腐蚀坑所呈现的形貌不同。研究中还发现利用KOH溶液腐蚀时能显现两种结构的腐蚀坑。离子束辐照过程中会产生大量的缺陷,这些缺陷与本征缺陷之间的相互作用使得辐照缺陷聚集在本征缺陷的周围,降低了本征缺陷区的化学腐蚀激活能,从而加快了本征缺陷区的腐蚀速率。由此推断,单个离子径迹在GaN中不能被腐蚀;低能重离子辐照能增强GaN本征缺陷区域的腐蚀。更多还原

【Abstract】 As the third generation semiconductor, GaN has attracted huge research interest due to its unique properties. It has great application and development prospects in the field of microelectronics and optoelectronics. Ion implantation has its great advantage in circuit fabrication for the integration of such devices. However, irradiation process inevitably produces lattice disorder that is detrimental to the device performance.In this dissertation, the damage accumulation in GaN crystal induced by low-heavy ion irradiation was studied. X-ray diffraction （XRD）, Rutherford Backscattering/ Channeling （RBS/C）, Atomic force microscopy （AFM） and Scanning electron microscopy （SEM） were utilized to study the damage and surface morphology in irradiated GaN. It is found that swelling occurred at an ion dose of 5×10¹⁴/cm² on the surface of the GaN after irradiated by 500keV Au⁺ ions. The higher the ion dose is the higher the swelling step height would be. Volatilization appeared on the surface of irradiated GaN after annealing at different temperatures. When annealed at 1000℃, it is found the step height between irradiated and unirradiated GaN is near the range of Au at energy of 500keV. In the study it is also found that GaN can be etched in AZ-400K photoresist developer and aqueous KOH at 80℃after irradiated by 100 or 500keV Au ions at ion doses from 1×10⁹/cm² to 5×10¹⁵/cm². With this method, defects in GaN films, after being irradiated by heavy ions, can be revealed with an etch pit density of 10⁶-10⁸/cm², far less than the irradiation ion dose but the similar magnitude with that in as-grown GaN films. Additionally, the etched pits present different features at different ion dose. Two different types of etch pits with different sizes can be observed when etched in aqueous KOH. Ion irradiation induced the appearance of new defects. The original defects in GaN could act as sinks to capture the produced defects by ion irradiation, which reduced the activation energy required for the etching of original defects in GaN. It indicates that single ion irradiation cannot be etched in GaN film and low-heavy ion irradiation can enhance the wet etching of GaN film at the sites having original defects.更多还原