Centimeter-long III-Nitride nanowires and continuous-wave pumped lasing enabled by graphically epitaxial lift-off

摘要

It remains a big challenge to elongate one-dimensional (1D) semiconductor nanowires (NWs),which can be attractive platforms for miniaturizing and/or integrating macroscopic devices,into centimeter-scale length.Herein,we report the innovative preparation of single-crystalline III-nitride NWs,with unprecedented length above 2 cm and the aspect ratio above 6000,by graphically epitaxial lifting-off (GELO) the epitaxial films on sapphire.The proposed GELO technology involves isotropic dry etching and selectively electrochemical (EC) etching.Reaction kinetics study of the EC etching indicate that two-steps processes are included,which is,to our best knowledge,firstly revealed and experimentally confirmed.Centimeter-long freestanding NWs,with predesigned structure of homogeneous GaN,p-GaN/(InGaN/GaN)_6 quantum-wells/n-GaN (simply InGaN/GaN QWs) and AlGaN/AlN/GaN heterostructure,are successfully obtained and exhibit superior morphological uniformity and robust flexibility.Optical properties of the released InGaN/GaN QW-NWs were well optimized owing to the relieved intrinsic strain.Random lasing behavior was unexpectedly observed by continuous-wave excitation of the individual InGaN/GaN QW-NW,with a low threshold of 232 kW?cm~(-2).This work represents a lowcost and economic approach to yield structure-engineerable super-long III-nitride NWs,which would promote the development and integration of optoelectronic nanodevices.