Photoassisted chemical smoothing of AlGaN surface after laser lift-off
Photoassisted chemical smoothing of AlGaN surface after laser lift-off
复制标题
激光剥离后 AlGaN 表面的光辅助化学平滑
DOI：
10.1116/6.0000192
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发表时间：
2020-07
影响因子：
1.4
通讯作者：
Baoping Zhang
中科院分区：
文献类型：
--
作者：
Zhongming Zheng;Hao Long;Samuel Matta;Mathieu Leroux;Julien Brault;Leiying Ying;Zhiwei Zheng;Baoping Zhang
为了制作AlGaN基垂直腔面发射激光二极管，要求一对表面光滑的分布布拉格反射器(DBR)具有高品质因数(Q)。在这项工作中，尝试了光辅助化学刻蚀(PCE)，以平滑-c(000-2)AlN表面后，通过激光剥离的方法去除蓝宝石衬底。首先，利用氙灯和KOH溶液对PCE的条件进行了优化。-c(000-2)AlN表面的均方根粗糙度从30.5 nm降低到5.6 nm，这使得我们能够在AlN表面上制备出更好的HfO2/SiO2DBR。然后，利用优化的PCE技术制备了改进的UV(Al，Ga)N平面微腔，并利用光致发光(PL)技术观察到了明显的腔模相关发射。通过比较PCE处理前后样品的光致发光光谱，确定了改进后的DBR在303 nm处的Q值从174增加到270。Q值的增加主要归因于光学腔内散射损耗的减小。并对PCE处理过程中表面改善的机理进行了讨论。因此，PCE被证明是一种提纯紫外氮化微腔质量的可行方法。
To fabricate AlGaN-based ultraviolet (UV) vertical cavity surface-emitting laser diodes, a pair of distributed Bragg reflectors (DBRs) having a smooth surface is desired to have a high quality factor (Q). In this work, photoassisted chemical etching (PCE) was attempted to smoothen the - c ( 000 - 2 ) AlN surface after removing the sapphire substrate by means of the laser lift-off process. First, the conditions for PCE were optimized using an Xe lamp and KOH solution. The root-mean-square roughness of the - c ( 000 - 2 ) AlN surface was reduced from 30.5 to 5.6 nm, which enables us to fabricate an improved HfO2/SiO2 DBR on the AlN surface. Then, using the optimized PCE technique, improved UV (Al,Ga)N planar microcavities were fabricated and distinct cavity-mode-related emissions were observed using the photoluminescence (PL) technique. By comparing the PL spectra between the samples with and without PCE treatment, the Q value at 303 nm for the case of the improved DBR was determined to increase from 174 to 270. The increase in the Q value is mainly attributed to the reduction of scattering losses in optical cavities. Furthermore, the discussion on the mechanism of improved surface during the PCE treatment is given. Consequently, PCE is demonstrated to be a feasible approach to refine the quality of ultraviolet nitride microcavities.