Surface effects on carrier dynamics: photoconductivity studies on Si (111)

Abstract

We correlate photoconductivity with surface characterization in order to probe the influence of different surface properties of Si ( 111) on electron-hole dynamics. Photoconductivity data show that the carrier recombination is influenced strongly by surface structure and chemistry as well as by trace imperfections which are undetectable by conventional surface characterization techniques. Results on the Si( 111) :As ( 1 x 1) surface indicate carrier recombination at this surface is negligible, in contrast to the (7X 7) reconstructed surface, where surface recombination is fast, with a surface recombination velocity measured to be >2 x lo6 cm/s. We also investigate the effect of sputter induced disorder and compare our finding with results from other techniques. Combining our results and the present understanding of the (7 x 7) electronic structure, we estimate the carrier capture cross section for dangling bonds to be -10 -l5 *

Dynamics and second-order nonlinear optical susceptibility of photoexcited carriers at Si(111) interfaces

“…Instead, we suggest that the increased density of surface states is responsible for the observed increase in SRV. 28 The more perfectly H-terminated Si͑111͒ surface has a longer decay time ͑Fig. 1͒, consistent with reduced number of defect states, confirming that surface recombination plays an important role in the relaxation of the photoexcited carriers.…”

Electrochemical Properties of (111)-Oriented n-Si Surfaces Derivatized with Covalently- Attached Alkyl Chains

“…Although the hydrogen-terminated Si surface has excellent electrical properties immediately after preparation, , this surface is quite susceptible to oxide growth in air or as a result of anodic current flow when in contact with water-containing electrolytes. − Such oxide growth not only degrades the electrical properties of the H-terminated silicon surface, but it also introduces a series resistance that impedes the operation of n-type Si electrodes in a photoelectrochemical cell . One of the goals of chemical modification of a photoanode is to prepare a molecularly well-defined protective interface that imparts improved stability to the surface while maintaining a high electrical quality of the semiconductor/liquid contact.…”

Stabilization of Si Photoanodes in Aqueous Electrolytes through Surface Alkylation

“…Semiconductors having band gaps between 0.9 and 1.7 eV are well-known to be optimal for use in photoelectrochemical solar energy conversion devices. , Si, with a band gap of 1.12 eV, is an especially attractive material for this application. The hydrogen-terminated Si surface obtained from wet chemical etching with HF(aq) is nearly electrically perfect when initially formed, , but this surface readily oxidizes in air or in water-containing ambients. The oxide not only introduces electrical defect states but also forms an insulating, passivating overlayer that quickly prevents photocurrent flow through an electrochemical cell. − …”