Musolino M, Tahraoui A, Fernández-Garrido S, Brandt O, Trampert A, Geelhaar L, Riechert H
Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin, Germany.
Nanotechnology. 2015 Feb 27;26(8):085605. doi: 10.1088/0957-4484/26/8/085605. Epub 2015 Feb 6.
AlN layers with thicknesses between 2 and 14 nm were grown on Si(111) substrates by molecular beam epitaxy. The effect of the AlN layer thickness on the morphology and nucleation time of spontaneously formed GaN nanowires (NWs) was investigated by scanning electron microscopy and line-of-sight quadrupole mass spectrometry, respectively. We observed that the alignment of the NWs grown on these layers improves with increasing layer thickness while their nucleation time decreases. Our results show that 4 nm is the smallest thickness of the AlN layer that allows the growth of well-aligned NWs with short nucleation time. Such an AlN buffer layer was successfully employed, together with a patterned SiOx mask, for the selective-area growth (SAG) of vertical GaN NWs. In addition, we fabricated light-emitting diodes (LEDs) from NW ensembles that were grown by means of self-organization phenomena on bare and on AlN-buffered Si substrates. A careful characterization of the optoelectronic properties of the two devices showed that the performance of NW-LEDs on bare and AlN-buffered Si is similar. Electrical conduction across the AlN buffer is facilitated by a high number of grain boundaries that were revealed by transmission electron microscopy. These results demonstrate that grainy AlN buffer layers on Si are compatible both with the SAG of GaN NWs and LED operation. Therefore, this study is a first step towards the fabrication of LEDs on Si substrates based on homogeneous NW ensembles.
通过分子束外延在Si(111)衬底上生长了厚度在2到14纳米之间的AlN层。分别利用扫描电子显微镜和视线四极质谱研究了AlN层厚度对自发形成的GaN纳米线（NWs）的形貌和成核时间的影响。我们观察到，在这些层上生长的NWs的排列随着层厚度的增加而改善，而成核时间则减少。我们的结果表明，4纳米是允许生长排列良好且成核时间短的NWs的AlN层的最小厚度。这样的AlN缓冲层与图案化的SiO x掩膜一起成功地用于垂直GaN NWs的选择性区域生长（SAG）。此外，我们用通过自组织现象在裸露的和AlN缓冲的Si衬底上生长的NWs集成体制作了发光二极管（LED）。对这两种器件的光电特性进行的仔细表征表明，在裸露的和AlN缓冲的Si上的NW-LED的性能相似。透射电子显微镜揭示的大量晶界促进了AlN缓冲层上的导电。这些结果表明，Si上的粒状AlN缓冲层与GaN NWs的SAG和LED操作都兼容。因此，本研究是朝着基于均匀NW集成体在Si衬底上制造LED迈出的第一步。
