Electrodeposition of Bi Thin Films on n-GaAs(111)B. II. Correlation between the Nucleation Process and the Structural and Electrical Properties

Abstract

The surface morphology and the crystal structure of 40 nm thin Bi films electrodeposited on GaAs(111)B at different growth overpotentials have been studied by means of atomic force microscopy and X-ray diffraction, respectively. The Bi/GaAs interface has also been electrically characterized by means of current-voltage curves that have been analyzed with the Thermionic-Field Emission Theory. Taking into account the results presented in Part I, we can conclude that the structural and electrical properties of the Bi layers are correlated with the nucleation process and, therefore, with the energy band diagram of the semiconductor-electrolyte interface. We have found that surface morphology is directly dependent on the amount of protons adsorbed on the GaAs surface, whereas the crystal quality and the interfacial properties also depend on the nucleation mechanism (instantaneous or progressive).

Electrodeposition of Bi films on H covered n-GaAs(111)B substrates

“…Figures 3a-e show AFM images obtained in each Bi film whereas Figure 3.f exhibits the evolution of the films rms with the overpotential. In all cases, the rms of the films is higher than that obtained for Bi films grown on Hads-free highly doped n-GaAs substrates [11], and decreases with ηSEI. At low overpotentials (ηSEI = -0.32 V and -0.37 V), porous Bi layers with rounded islands and a rms of around 9-10 nm are obtained (Figure 3a-b and f).…”

“…In order to implement Bi in electronic devices, semiconductors like GaAs can be very versatile for several reasons. Tunnel [10,11] or rectifying [12] Schottky barriers can be obtained by varying the substrate doping level, leading to different mechanisms for electron transport through the interface, thermionic-field emission or thermionic emission, respectively. Moreover, modifying the substrate surface orientation it is possible to synthesize Bi thin films with different crystalline textures and interfacial electrical properties [10].…”

“…Although it might protect the n-GaAs surface from oxidation, it will hinder the nucleation of Bi(III) ions avoiding the growth of compact and high quality Bi thin films [13]. To solve this problem, we designed a procedure that desorbs the Hads layer before performing the growth of the Bi layer, so high-quality films can be obtained [14,10,11]. Nevertheless, this protocol involves the dissolution of an initial Bi deposit and, therefore, it can only be used with highly-doped semiconducting substrates with a carrier concentration higher than 2•10 17 cm -3 .…”

“…We showed the strong impact that the growth overpotential has on the properties of Bi layers electrodeposited at constant potential on Hads-free highly doped n-GaAs(111)B substrates [11,9]. We reported that the morphological, structural and interfacial electrical properties are clearly correlated with the nucleation process which is in turn correlated with the energy band diagram of the semiconductor-electrolyte interface (SEI).…”

Influence of Bi on dielectric properties of GaAs1−xBix alloys

“…In the literature [7,8], several works have been focused on the study of the impact of laser irradiation on GaAsBi/GaAs quantum wells, band structure, photovoltaic characterization, structural and electronic properties of GaAsBi. The effect of Bi in Bi-doped GaAs barrier layers on the structural and optical properties of * E-mail: deger@istanbul.edu.tr InAs/GaAs quantum-dot heterostructures has been studied [9], while the study on the correlation between overpotential and nucleation process, nucleation process and structural, electrical properties has been reported in another works [10,11]. Besides, the nonlinear optical properties of GaAsBi semiconductor have been reported in the literature [12].…”