A New Process for Optical Data Recording by Photoelectrochemical Etching

Abstract

Photoetching of holographic gratings was performed on materials belonging to two families of compounds, exhibiting bidimensional and tridimensional structures. Fringes of poor quality only could be obtained on the Van der Waals face of quasi‐two dimensional (layered) semiconductors due to their high resistance to photocorrosion (WSe2), or large diffusion length of minority carriers along this face (InSe), while good morphological and optical contrasts were obtained on the surface of II — VI semiconductors. — Using a laser scanning setup, the photoresponse of Schottky diodes which were made from these semiconductors was used to convert optical information into electrical signal. The photoetched part exhibits an improved photoresponse, which produces electrical contrast between the two parts. This observation is used to transform optical information into an electrical signal. The diffusion length of minority carriers was determined from this photocurrent profile. Some applications for this method for holography and for optical data recording and its retrieval are discussed. Guidelines for materials' selection for this kind of application are proposed.

(Research Award of the Energy and Technology Division) (Photo)Electrochemistry in the Service of Solar Energy Conversion

“…The photoelectrochemical etching of single crystal and polycrystalline semiconductors, was initiated in order to study the properties of a variety of semiconductors when they were etched under controlled conditions. This work which started as purely academic endeavor has spanned over more than twenty years, with studies of II-VI compounds and lamellar [13][14][15]. The research in photoelectrochemistry included silicon as an electrode material [16,17].…”

Hole Diffusion Length Measurement for n‐type Semiconductors by Using Photoelectrochemical Etching Technique

“…Assuming that the electrochemical etching rate r(x) as a function of the position x is proportional to excess hole concentration at the surface, Ap(x, 0), we get r(x) = CAp(x, 0) [8] where C is a proportionality constant. Then, a relationship between etched depth d(x) and excess hole concentration at the surface hp(x, 0) is…”

“…Therefore, we can get information about the hole-diffusion length from the photoelectrochemical etching profiles. Ryan et al (8) estimated a hole diffusion length from a fringe pattern recorded on a compound semiconductor such as CdSe with a holographic photoetching technique.…”