阴极荧光联合分析系统在III族氮化物研究中的应用

Research Applications in III-nitrides with Cathodoluminescence Unitized Systems

利用高性能阴极荧光(CL)联合分析系统对几类典型的III族氮化物材料进行测试分析.在光谱研究中,利用CL紫外可见光谱系统,对c面蓝宝石衬底上生长的AlxGa1-xN薄膜进行阴极荧光单色谱测试分析,揭示了CL的激发强度与发光带之间的变化关系.进一步研究了掺Mg的Al0.5Ga0.5N薄膜的带边和杂质能级发光机理.利用CL近红外光谱系统对InN薄膜的阴极发光特性进行了研究,验证了InN实际光学带边Eg在0.77eV附近.利用微区分析(CLmapping)系统,可在紫外波段确切地给出材料不同波长的荧光发光区这一特点,对HVPE生长的自支撑GaN衬底进行了SEM和CL微区的对比分析,研究了GaN的位错类型和分布.

The optical properties of several typical Ⅲ-nitride semiconductors were investigated by cathodoluminescence （CL） unitized systems. The CL unitized systems are combined with a thermal field-emission scanning electron microscopy （JEOL JSM-7000F） and a high performance CL spectroscopy （Gatan Mono CL3） equipped LN-cooling stage. Two aspects can be obtained from the measurements： （1） CL spectrum. Using a UV-visible CL spectrum system, the optical properties of unintentionally-doped and Mg- doped Alx Ga1-x N films grown on c-plane sapphire are analyzed. This analysis indicates that the peak intensity of near band edge emission at 4.6eV increases proportionally with excitation power density. However, that the intensity of the 3.9eV band originated from a Mg-doped impurity-level shows saturation independence with excitation power density. Furthermore, the CL from InN films is measured with a near infrared （NIR） CL system,which proves that the optical band gap of InN locates at 0. 77eV. （2） CL mapping. The CL unitized systems can give the luminescence area at different wavelength in the UV-visible range. The free-standing GaN substrates grown by hydride vapor phase epitaxy are analyzed combining SEM and CL mapping methods. The edge type dislocations are observed under the surface using CL mapping instead of SEM. The type,distribution,and luminescence properties of dislocations are studied.