Anodically Induced Chemical Etching of GaAs Wafers for a GaAs Nanowire-Based Flexible Terahertz Wave Emitter

Abstract

A generic top-down approach for the preparation of extended arrays of high-aspect ratio GaAs nanowires (NWs) with different crystallographic orientations (i.e., [100] or [111]) and morphologies (i.e., porous, nonporous, tapered, or awl-like NWs) is reported. The method is based on the anodically induced chemical etching (AICE) of GaAs wafers in an oxidant-free aqueous HF solution at room temperature by using a patterned metal mesh and allows us to overcome the drawbacks of conventional metal-assisted chemical etching (MACE) processes. Local oxidative dissolution of GaAs in contact with a metal is achieved by externally injecting holes (h + ) into the valence band (VB) of GaAs through the metal mesh. It is found that injection of holes (h + ) through direct GaAs contact, rather than the metal mesh, does not yield uniform nanowires but porosify GaAs wafers due to the high cell potential. On the basis of experiments and numerical simulation for the spatial distribution of an electric field, a phenomenological model that explains the formation of GaAs NWs and their porosification behaviors is proposed. GaAs NWs exhibit excellent terahertz (THz) wave emission properties, which vary with either the length or the shape of the nanowires. By taking advantage of controlled porosification and easy transfer of GaAs NWs to foreign substrates, a flexible THz wave emitter is realized.

Ultrasonic‐Assisted Electrochemical Nanoimprint Lithography: Forcing Mass Transfer to Enhance the Localized Etching Rate of GaAs

“…[24] Additionally, the etching kinetics can be modulated through the application of an external applied potential. [25][26] More importantly, the mass transfer and mass balance are one of the major issues to be solved as the etching reaction occurs in the ultrathin electrolyte layer between the imprint mold and the semiconductor wafer during the ECNL process. [23][24] To tackle this issue, a porous mold was adopted to provide additional mass transfer channels.…”

“…One method involves leveraging the photoelectric effect, which promotes the separation between holes and electrons in GaAs, thereby enhancing the contact electric field at the Pt/GaAs interface and improving the etching rate of GaAs during ECNL process [24] . Additionally, the etching kinetics can be modulated through the application of an external applied potential [25–26] . More importantly, the mass transfer and mass balance are one of the major issues to be solved as the etching reaction occurs in the ultrathin electrolyte layer between the imprint mold and the semiconductor wafer during the ECNL process [23–24] .…”

Enhanced terahertz emission from mushroom-shaped InAs nanowire network induced by linear and nonlinear optical effects

“…Moreover, NWs have tunable length, diameter, directionality, and density so that the THz emission properties can be further adjusted. Therefore, THz emission from many semiconductor NWs have been demonstrated, such as Si [23], Ge [24], GaN [25], GaAs [22,26], InP [27], Bi 2 Te 2 Se [28] and AlGaAs [29]. Particularly, several works have intensively reported the THz emission phenomena from InAs NWs.…”

On the operating mechanisms of flexible microwave inductors and capacitors under mechanical bending conditions

“…For flexible electronics, inorganic single-crystal materials can be processed into nanomembranes only hundreds of nanometers thick by utilizing the methods of reactive ion etching (RIE), wet etching, and transfer techniques. These inorganic single-crystal nanomembranes with high carrier mobilities are thus perfect candidates for flexible wireless communication circuits, and could be compatible with current complementary metal-oxide semiconductor (CMOS) processes [11][12][13][14][15][16]. Recently, a variety of flexible active components (e.g.…”