(Invited) Direct Electrodeposition of Crystalline III-V Semiconductor Films

This presentation will describe our latest results on the concept of using liquid metal electrodes as platforms for direct electrodeposition of crystalline inorganic semiconductor materials at comparatively low temperatures.

Large scale production of crystalline thin films of III-V semiconductors is challenging in two ways. First, the majority of synthetic methods are energy- and resource-intensive. For example, vapor phase crystal growth techniques such as metal-organic vapor phase epitaxy and molecular beam epitaxy  involve ultra-high vacuum (UHV) equipment and temperatures above 400 °C. Similarly, liquid phase epitaxy requires sustained temperatures in excess of 750 °C and pressurized furnaces. Second, these same fabrication methods can be difficult to incorporate directly into device fabrication processes. For example, high temperatures and corrosive reagents can damage delicate electronic device architectures (e.g. complementary metal-oxide-semiconductor (CMOS)) and sensitive platforms (e.g. plastics). As a result, cumbersome and costly transfer and integration steps are necessary. Electrodeposition of III-V semiconductors has been extensively investigated since electrochemistry offers precise control of (heterogeneous) reaction rates and simple process electronics and equipment (i.e. a current or potential source and a beaker). However, stoichiometry, purity, and crystallinity have proven difficult to control.

Here, experimental data will be shown for a new tactic that offers the purity and quality of aforementioned high temperature, vapor-phase syntheses with the simplicity and affordability of conventional electrodeposition. Specifically, data will be presented that illustrates the preparation of polycrystalline films of GaAs, GaSb, InAs, InSb, and alloys thereof through an electrochemical liquid-liquid-solid (ec-LLS) process. Chronoamperometic and voltammetric responses recorded during ec-LLS will be shown. Materials characterization data in the form of electron & X-ray diffraction, X-ray photoelectron & Raman spectroscopies, and optical & electron microscopies will be also be discussed. Comparisons and distinctions with other, previously demonstrated electrochemical, chemical vapor deposition, and chemical metallurgical processes will be presented. The prospects for making high quality (epitaxial) III-V films and for seemless incorporation of III-V films on sensitive device platforms through ec-LLS will be discussed.