Fluctuation model for a rough metal/semiconductor interface

Abstract

The fluctuation model with Gaussian-type of barrier heights distribution that was recently applied successfully to explain the dark current -voltage characteristics of Au/GaAs barrier structure with microrelief interface, in this paper is extended to photoelectric characteristics. In addition to the change of the Richardson constant and the apparent temperature coefficient of barrier height we predict the decrease of the open-circuit voltage of photodetectors or solar cells. The theoretical predictions have been verified experimentally on the Au/GaAs Schottky barriers with dendrite-like or quasigrating interface prepared by wet anisotropic etching.1. Introduction Micro/nanorelief metal/semiconductor (MS) interfaces are usually used for a reduction of light reflection and for increase of photocurrent of surface-barrier structures. However, the geometric disorder of such interfaces leads to the worsening of their electronic structure due to the change in their microstructure. The electrical behavior of corresponding Schottky diodes was explained by a two phase (or patch) model with different barrier heights [1]. As a result, in the diodes with rough interfaces the dominating current transport mechanism changes from thermionic emission to thermionic-field emission, the barrier height decreases and its temperature dependence increases. Often some additional treatments are used for smoothing the microrelief. In this case metal/semiconductor barrier can be modeled by a continuous set of diodes with different barrier heights connected in parallel. Several types of barrier height distribution (Gaussian type [2 -5], log-normal [6,7] or their superposition) have been proposed to describe the electrical characteristics of Schottky diodes and have been analyzed to determine the conditions of their suitability [4,7,8]. This fluctuation model with the barrier heights distributed according to Gaussian formula recently was applied successfully to explain the dark current-voltage characteristics of Au/GaAs microrelief interface, prepared by wet chemical anisotropic etching [5].In this work this fluctuation model is extended to photoelectric characteristics of such nonhomogeneous MS interfaces, which are compared with experimental results obtained on Au/GaAs Schottky barriers with dendrite-like or quasi-grating interface.

Efficiency enhancement of surface barrier solar cells due to excitation of surface plasmon polaritons

“…To estimate the V OC value in the case of a non-flat interface of SBH, we used the results of [7,8] for a randomly rough MS interface. Therefore, V OC has been obtained by the following expression:…”

“…where n is the non-ideality factor, K ph = J SC /J 0 SC , φ B is the decrease of the barrier height of the microrelief interface in comparison with the flat one. The essential increase of J SC due to nanoscale relief is presented in figure 8, where the internal quantum efficiency from figure 7 was used to average equation (7). The value K ph ≈ 2 has been obtained.…”

“…• In thin film SCs, the subwavelength scatterers can couple sunlight into guided modes in the semiconductor layer, when the back interface is coated with a corrugated metal film [5,6]; this shows the design of ultrathin SCs that exhibit enhanced absorption. • The light scattering from metal nanoparticles near their local (surface) plasmons (SPs) excitation is also a promising way to increase the light absorption [7,8] in thin film SCs or the enhancement of electroluminescence in thin Si-on-insulator light-emitting diodes [12]. Two basic mechanisms have been proposed to explain photocurrent enhancement by metal nanoparticles incorporated into SC: light scattering and near-field concentration of light.…”

“…Due to enhancement of the light transmittance to the absorptive layer of SBH with periodical microrelief, the shortcircuit photocurrent J SC increases, but at the same time both the lateral inhomogeneity of the emitter layer and the increase of its area can lead to the decrease of the open-circuit voltage V OC [7,8], since the surface recombination rate increases. Moreover, the short-circuit photocurrent can change with increasing the interface area and the related increasing of the surface recombination rate as well as rates of other interface electron/hole transitions.…”

Modification of Optical Properties of Porous AIIIBV Layers Produced by Anodic Etching

“…For A III B V semiconductor compounds (GaAs, InP, InAs, GaP, GaSb, etc. ), many effective methods of electrochemical etching have been elaborated [2,3,[7][8][9][10]. In addition, the electrochemical method for microrelief (porous) surface preparation allows one to change the statistical geometrical parameters of a surface microrelief in a wide range.…”