Fang Z L, Lin D Q, Kang J Y, Kong J F, Shen W Z
Semiconductor Photonics Research Center, Department of Physics, Xiamen University, Xiamen 361005, People's Republic of China.
Nanotechnology. 2009 Jun 10;20(23):235401. doi: 10.1088/0957-4484/20/23/235401. Epub 2009 May 18.
Interface modification by inserting an ultrathin low-temperature GaN layer prior to the growth of high-temperature GaN barriers followed by an annealing process was employed to improve the properties of the InGaN/GaN quantum wells. By detailed studies and comparisons of the surface morphology, photoluminescence and the surface compositions of the InGaN/GaN quantum wells at different growth stages with and without the interface modification, we find that with the interface modification the surface morphology was significantly improved with better smoothness, and smaller and shallower pits of lower density compared with that without interface modification; further, the indium aggregation and phase separation were suppressed. The physical phenomena are attributed to the 'strain pre-relief effect' by the formation of quasi-dots (approximately 20 nm in diameter) prior to temperature ramping and growth of high-temperature GaN barriers. Furthermore, the ultrathin low-temperature GaN layers have a good protection property as confirmed by PL and XPS measurements.
通过在生长高温GaN势垒之前插入超薄低温GaN层并随后进行退火处理来进行界面改性，以改善InGaN/GaN量子阱的性能。通过对有无界面改性的不同生长阶段的InGaN/GaN量子阱的表面形貌、光致发光和表面成分进行详细研究和比较，我们发现，通过界面改性，表面形貌得到显著改善，平整度更好，与未进行界面改性相比，坑更小、更浅且密度更低；此外，铟的聚集和相分离受到抑制。这些物理现象归因于在高温GaN势垒升温及生长之前形成准点（直径约20 nm）所产生的“应变预释放效应”。此外，如PL和XPS测量所证实的，超薄低温GaN层具有良好的保护性能。
