Low dimensional freestanding semiconductors for flexible optoelectronics: materials, synthesis, process, and applications

Abstract

In this review, the primary focus is the recent advances in the development of freestanding inorganic crystalline semiconductors and their manipulation technology for flexible optoelectronic applications. We firstly cover the details of the growth and processing techniques of freestanding inorganic crystalline semiconductors in various dimensions and their material property under strain condition. Finally, fabrication processes and opto-electrical properties of flexible optoelectronics are introduced. Future research directions are also discussed, including further enhancement of device performance, building more types of optoelectronic devices on flexible substrates, and process integration for the advanced optoelectronic circuits and systems.

In(Ga)N Nanostructures and Devices Grown by Molecular Beam Epitaxy and Metal-Assisted Photochemical Etching

“…GaN membranes have been prepared via diverse processes: laser [ 82 ], chemical [ 83 ], electrochemical [ 84 , 85 ], and mechanical lift-off from suitable buffer layers [ 86 , 87 ]. However, the direct growth of inorganic NWs on flexible substrates is hampered by interfacial reactions between the grown nanowires and flexible metallic substrates and the low melting temperatures of flexible organic substrates [ 88 ]. Doan et al lifted an InGaN/GaN LED from a sapphire surface using a 248-nm KrF excimer laser [ 89 ].…”

Strain-free GeSn nanomembranes enabled by transfer-printing techniques for advanced optoelectronic applications

“…In this paper, we present a new strategy to achieve strain-free GeSn alloys via a transfer-printing of nanomembranes (NMs). Single-crystalline semiconductor NMs are transferrable free-standing thin films with unique advantages such as excellent mechanical flexibility and material quality (e.g., high mobility and light absorption) [33][34][35][36][37][38]. By transferprinting the GeSn NMs and removing the Ge buffer layer, the compressive strain that was initially stored in the GeSn was successfully removed.…”

PIC-integrable, uniformly tensile-strained Ge-on-insulator photodiodes enabled by recessed SiNx stressor

“…However, considering feasible complementary metal oxide semiconductor (CMOS) integration for photonic-integrated circuits (PICs), a trade-off can arise between the strain uniformity and the integration compatibility with PICs. Prior studies have extensively employed substrate undercut [7,8], removal [9,10] or layer transfer to flexible substrates [11,12] to facilitate both an optimal strain magnitude and uniformity for the materials of interest. However, this poses challenges of electrical interconnections between Si CMOS circuits and the strained materials.…”