Electrochemical Manufacturing of a p-n Junction Employing Water Solutions

Abstract

Our society relies on the use of semiconductor devices, which are, so far, fabricated using expensive and complex processes requiring ultra-high vacuum equipment. Here we report on the possibility of growing a p-n junction taking advantage of electrochemical processes based on the use of aqueous solutions. The growth of the junction has been carried out using the Electrochemical Atomic Layer Deposition (E-ALD) technique, which allowed us to sequentially deposit two different semiconductors, CdS and Cu2S on a Ag(111) substrate, using water based solutions containing Cd2+, Ag+ and S2- precursors [1,2]. The main problem, encountered when growing this kind of systems, is related to the unattainable electrochemical characterization of the deposition conditions for the different elements without altering the already deposited layers.This problem was overcome by performing an in-situ x-ray characterization of the grown layers during the E-ALD process. By this procedure, we were able to find the conditions at which the deposition resulted in the formation of thin layers with crystallographic ordered structures and reduced surface/interface roughness. The electronic transport properties of samples, made of 9 nm of Cu2S on top of 10 nm of CdS, have then been determined ex-situ. The samples showed a good stability in air and the I-V characteristic, measured in several positions of the sample, to investigate the homogeneity of the response, is the one typical of a diode.The present study is funded by the PRIN Project (“Progetti di Ricerca di Rilevante Interesse Nazionale”), “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)”, grant number 2017YH9MRK.