Effect of Gallium Doping on the Characteristic Properties of Polycrystalline Cadmium Telluride Thin Film

Abstract

Ga-doped CdTe polycrystalline thin films were successfully electrodeposited on glass/fluorine doped tin oxide substrates from aqueous electrolytes containing cadmium nitrate (Cd(NO 3 ) 2 AE4H 2 O) and tellurium oxide (TeO 2 ). The effects of different Ga-doping concentrations on the CdTe:Ga coupled with different post-growth treatments were studied by analysing the structural, optical, morphological and electronic properties of the deposited layers using x-ray diffraction (XRD), ultraviolet-visible spectrophotometry, scanning electron microscopy, photoelectrochemical cell measurement and direct-current conductivity test respectively. XRD results show diminishing (111)C CdTe peak above 20 ppm Ga-doping and the appearance of (301)M GaTe diffraction above 50 ppm Ga-doping indicating the formation of two phases; CdTe and GaTe. Although, reductions in the absorption edge slopes were observed above 20 ppm Ga-doping for the as-deposited CdTe:Ga layer, no obvious influence on the energy gap of CdTe films with Ga-doping were detected. Morphologically, reductions in grain size were observed at 50 ppm Ga-doping and above with high pinhole density within the layer. For the as-deposited CdTe:Ga layers, conduction type change from n-to p-were observed at 50 ppm, while the n-type conductivity were retained after post-growth treatment. Highest conductivity was observed at 20 ppm Ga-doping of CdTe. These results are systematically reported in this paper.

Electroplating of Semiconductor Materials for Applications in Large Area Electronics: A Review

“…This ability provides the ease of bandgap engineering of semiconductor material such as CuInGaSe 2 between~1.00 and 2.20 eV. Extrinsically, this observation has also been documented for electroplated binary semiconductor materials such as CdTe doped with Ga [65] amongst others. The bandgap of the resulting doped semiconductor directly affected the incorporated dopant even at the parts per million level [65,71].…”

“…It should be noted that even with a high purity precursor with 99.999% purity, it can carry an impurity level of 10 ppm. Purification is essential due to the effect of impurities even in ppm levels [65] on the characteristic properties of electroplated semiconductor materials. It should be noted that electro-purification of a bath must be performed using similar deposition parameters (such as bath temperature, pH, stirring rate, etc.)…”

“…While a reduction in the cathodic voltage of the CuInGaSe2 results in the reduction of bandgap due to the richness of Cu [42] (see Figure 5). This ability provides the ease of bandgap engineering of semiconductor material such as CuInGaSe2 between ~1.00 and The ease of intrinsic doping and the effect of extrinsic doping of electroplated semiconductor materials have been well established in the literature [65,71]. Due to the simplicity of ED, doping at the ppm level is made possible [65,71,72].…”

Electroplating of Electronic Materials for Applications in Large Area Electronics: A Review

“…Note the ability to grow p + ,p, i, n and n + materials from the same electrolyte, simply by varying the deposition voltage[56][57][58]. ease of intrinsic doping and the effect of extrinsic doping of electroplated semiconductor materials have been well established in the literature[52,60]. Due to the simplicity of ED, doping at parts-per-million (ppm) level is made possible[52,60,61].4.1.3 Bandgap engineering capabilityThe Control or alteration of the bandgap of materials (with emphasis on semiconductor) is easily achievable in electrodeposition technique.…”

“…ease of intrinsic doping and the effect of extrinsic doping of electroplated semiconductor materials have been well established in the literature[52,60]. Due to the simplicity of ED, doping at parts-per-million (ppm) level is made possible[52,60,61].4.1.3 Bandgap engineering capabilityThe Control or alteration of the bandgap of materials (with emphasis on semiconductor) is easily achievable in electrodeposition technique. Typically, this can be achieved by controlling the atomic composition of the elemental component of the semiconductor material.…”