XPS investigation of anodic oxides grown on p‐type InP

Abstract

Chemical composition of anodic oxides grown on lightly doped ptype InP have been investigated by XPS. Anodization was performed in the constant current density (J,) mode using an ortho-phosphoric acid solution mixed with acetonitrile (ACN). The electrolyte was chosen after experimentation on the effect of the anudiition parameters (electrolyte, viscosity of the electrolyte and pH, J, and illumination level) and annealing conditions on the uniformity and stability of the oxide and the contamination level, as determined by SEMPDAX, SIMS and XPS. Based on our XPS investigation, it appears that the inhomogeneity with depth of the anudii oxides grown on ptype InP is strongly dependent on the growth conditions. Depending on the anodization procedure, the anodic oxide In recent years, indium phosphide has proved to be a very promising semiconductor material for various applications owing to its intrinsic properties, such as high electron mobility and high radiation tolerance. Hence, major attention is beginning to be devoted to InP owing to its potential applications, such as highspeed electronic and integrated opto-electronic devices and high-performance radiation-resistant space solar cells. All these applications are not yet technologically mature and more studies are needed before highperformance devices can be realized.One of the major problems yet to be solved in InP technology is to form insulators on the InP surface that have good chemical stability and dielectric and interface properties. Such insulators are needed in applications requiring surface passivation and for selective etching during device fabrication. Surface passivation is obtained by growth of an insulating layer (extrinsic passivation), which compensates the surface states so that the surface recombination velocity (SRV) is greatly reduced.Based on previously reported information on the insulators formed on InP (e.g. as gate insulators for MISFETS),'-3 the ideal insulator for surface passivation and selective etching should have the following bulk and interfacial properties:

X-Ray Photoelectron Study of Yb-Doped InP

“…Taking into account the above evidence ( Figs. 1 and 2, Table) and the literature data [5] one can conclude that in a surface-and subsurface region of InP, accessible to XPS, there is a noticeable (although minor) influence of different native oxide species.…”

“…In particular, the peak E1 (0 1s) is due to the presence of indium oxide (In2O3) [5]. The parameters (energy, FWHM) of the peak 2 from the O is spectrum indicate that it probably results from superposition of the contributions given by In(OH) 3, In(OH)3 • xH2O, In2O3 as well as the phosphate species like InPO4 and InPO4 • xH2 0 [5].…”

“…1) is readily observed as a doublet. One can distinguish there the main peak at 128.7 eV ascribed to P in InP (bulk component), and the minor peak around 133.6 eV (surface component), which is indicative of phosphorus bound in phosphates, introduced by surface oxidation (see [4,5,7]). …”

“…2a) exhibits an asymmetric shape, characteristic for an overlap of bulk-and surface-component peaks [4,5]. Its numerical analysis, performed by fitting with Gaussian-Lorentzian peaks, enabled us to distinguish the dominant bulk-related peak (EB = 444.2 eV) from the weaker surface-related contribution (EB = 445.1 eV).…”

“…[4][5][6]. In the case of Yb-doped InP, there is a lack of reports concerning XPS investigations (see Ref.…”