纳米柱高度对GaN基绿光LED光致发光谱的影响

纳米柱结构是释放高In组分InGaN/GaN绿光LED量子阱层应变的有效方法。本文采用自组装的聚苯乙烯微球掩模、感应耦合等离子体干法刻蚀和KOH溶液的湿法腐蚀,在GaN基绿光LED外延片上制备了3种高度的纳米柱结构,通过扫描电子显微镜观察纳米柱结构的形貌,并测试了常温和10 K低温时的光致发光谱(PL)。结果表明:应变释放对压电场的影响显著,使得纳米柱结构样品的内量子效率(IQE)提高,PL谱峰值波长蓝移;应变在量子阱中的不均匀分布还使得PL谱半高全宽(FWHM)展宽。与普通平面结构相比,高度为747 nm的纳米柱结构可使得IQE提升917%,PL谱峰值波长蓝移18 nm、FWHM展宽7 nm。另外,纳米柱结构样品的有源区有效面积减小可使得PL谱FWHM减小。

Effects of The Height of Nanorod Structure on The Photoluminescence Spectra of GaN-based Green LED

Nanorod structure is an effective method to release the strain in multiple quantum wells of In-GaN/GaN green LED with high In component. In this paper, the natural lithography with self-assembled polystyrene microspheres, inductively coupled plasma dry etching and wet-etching using KOH aqueous solution were used to fabricate the nanorod structure with three heights in GaN-based green LED epitaxial wafers. The morphology was observed by scanning electron microscope, and the photoluminescence (PL) spectra at room temperature and 10 K low temperature were characterized. It is shown that the strain re-laxation significantly affect the piezoelectric field, thereby the nanorod structure leads to a promotion of the wafers'internal quantum efficiency (IQE) and blue-shift of the peak wavelengths of PL spectra, and the nonuniform distribution of the strain causes a broadening of the FWHM ( full width at half maxi-mum). Compared with the ordinary planar structure, the nanorod structure with the height of 747 nm in-duces an enhancement of 917% for the IQE, a blue-shift of 18 nm for the peak wavelengths of PL spec-trum, and a broadening of 7 nm for the FWHM. The results also indicate that the decreasing of effective active area of samples with nanorod structure may reduce the FWHM.