摘要
首次报道了用不同浓度的Ａｌ离子注入于蓝宝石衬底上的ＧａＮ薄膜（注入能量为５００ｋｅＶ、注入浓度为１０１４～１０１５ ｃｍ－２）， 在做了不同温度和不同时间的快速热退火处理以及常规热退火处理后，在１２Ｋ下用Ｈｅ－Ｃｄ 激光（３２５ｎｍ）激发得到其发射谱。结果显示， 经大剂量Ａｌ注入后的样品，其光致发光谱中３．４５ｅＶ的带边激子发光以及２．９ ～ ３．３ｅＶ的４个声子伴随峰消失。此表明大剂量Ａｌ注入对ＧａＮ的晶体结构造成严重的损伤，以致本征发光消失。经１０１４ｃｍ－２剂量Ａｌ注入后的样品，在Ｎ２气氛中退火处理后，２．２ｅＶ缺陷发光峰得到了一定程度的恢复。而且，经常规退火处理后，此发射峰比快速退火处理的样品发射峰恢复得更好（其积分光强高３倍）。相似的结果亦显示于１０１５ ｃｍ－２ 浓度的Ａｌ 注入的样品。２．２ｅＶ 黄色荧光源于ＧａＮ的缺陷（如Ｇａ空位（ＶＧａ）， 或ＶＧａＨ２，或ＶＧａ－ＯＮ 复合体），其能级位于价带顶以上约１．１ｅＶ处。荧光发射可以来自"导带缺陷能级"的跃迁，也可能来自浅施主（如Ｎ位Ｏ，能级位于导带下～１０ ｍｅＶ）至上述缺陷能级之间的跃迁。Ｉ－Ｖ 测量显示，Ａｌ的注入区成为 ～ １０?
Ion implantation is one of the most commonly used processes in semiconductor technology. It is particularly useful for achieving a laterally varying doping concentration profile across a semiconductor wafer or a film. Al has been widely used in producing ternary compound AlxGa1-x N, which is very important in such devices as high temperature transistors and UV detectors. However, it appears that study concentrated on Al implantation into the GaN and related devices has not yet been made. It is main aim of this paper to report on some such studies of the optical characteristics of Alimplanted (implantation energy and dose: 500keV and 1014- 1015cm-2, respectively) GaN grown on sapphire. Photoluminescence (FL) spectra taken at 12K on as-grown and implanted GaN show that the band edge exciton emission (corresponding 3. 45eV) and four phonon replica peaks ( 2. 97-3. 25eV) disappear for the implanted samples even after annealing, which suggests that it is the high-dose implantation that causes serious damage to the crystal structure of GaN. For the samples implanted by 1014 cm-2 dose, the 2. 2eV PL structure almost eliminates in the as-implanted samples but may recover under a certain circumstance after annealing in N2 atmosphere. Compared to rapid thermal annealing (RTA) (1 000℃ , 10-20s. ), normally annealing (850℃, 20mm) appears to be advantage in recovering the 2. 2eV emission peak with the integral light intensity three times than RTA samples. Similar results are also obtained from the samples implanted with 1015 cm2 dose. 2. 2eV yellow luminescence (YL) is from the defects such as Ga vacancy (VGa), or VGa- H2, or VGa-ON complex, with the energy level(s) located at about 1.1eV above the valence band. Therefore, YL may not only be from the transitions between the conduction band and the defect levels, but also from the transitions between shallow donors and the defect levels, such as nitride-site oxygen with the activation energy about 10 meV below the conduction band. The I-V measurement shows that the implanted area became a high resistance film with the line resistivity as high as 1012 Ω· cm-1 which indicates some Al+ implantation-induced deep electron traps. The conductive electron could be seized by such traps, which led to the luminescence emission disappeared. However, some such defects can be annealed under a certain heat treatment process, therefore the 2. 2eV emission peak can be partly recovered.
出处
《液晶与显示》
CAS
CSCD
2002年第2期84-91,共8页
Chinese Journal of Liquid Crystals and Displays
基金
中国博士后基金会暨王宽诚基金会资助项目 (1999No.5
2000No.17)
安徽省自然科学基金资助项目(0046506
