The mechanism of (Hg,Cd)Te anodic oxidation

Janousek, Bruce K.; Carscallen, Richard C.

doi:10.1063/1.331639

Cited by 31 publications

(23 citation statements)

References 9 publications

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“…The initial stages of the oxide film growth have long been considered to occur by a dissolution-precipitation mechanism [9]. On scanning the potential positive, dissolution of the semiconductor surface continues at an increasing rate until the concentration of the dissolved species approaches its solubility limit.…”

Section: Anodic Oxide Growthmentioning

confidence: 99%

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Enhancement of the second harmonic signal from Hg1−xCdxTe (MCT) in the presence of an anodic oxide film

Wark

McErlean

Cruickshank

et al. 2010

Journal of Electroanalytical Chemistry

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a b s t r a c tSecond harmonic generation (SHG) is now widely regarded as a valuable tool for investigating electrode surfaces. Typically, most studies have been limited to substrates which lack bulk symmetry and monitoring events such as sub-monolayer formation and surface reconstruction. Here, the development of a model that can be used to quantitatively describe the enhanced SH signal observed in the presence of an anodic oxide film on a non-centrosymmetric substrate, Hg 1Àx Cd x Te (MCT), is described. The aim is to further expand the utility of SHG for probing different electrode systems. The growth of the high quality oxide films was first followed by in situ ellipsometry. For thin films (<100 nm) grown at a constant current density of 150 lA cm À2 , an effectively uniform oxide layer is found with a refractive index n of $2.15 ± 0.05 and exhibiting no absorption of the incident radiation at 632.8 nm (1.96 eV). In the presence of such an oxide film of 58 nm thickness, the second harmonic (SH) signal intensity measured in reflection is found to be significantly enhanced in both the P IN -P OUT and P IN -S OUT polarisation configurations. To quantify the changes observed, each layer in the model is assigned its own symmetry and optical constants at the fundamental, x and harmonic X (= 2x) frequencies and a defined thickness. Modeling of the SH rotational anisotropy experiments carried out at different angles of incidence indicated that most of this increase could be accounted for by multiple reflections of the fundamental wave x = 1064 nm (1.17 eV) in the composite ambient/oxide/MCT layer, with little contribution from charge accumulation at the buried MCT/oxide interface for this oxide thickness.

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Section: Anodic Oxide Growthmentioning

confidence: 99%

“…During the electrochemical formation of the anodic oxide layer, the MCT substrate material is consumed and sharp interfaces have thus been reported to form [2]. Oxide growth is usually carried out using the well established constant current anodisation method [5,9,10] in 0.1 M KOH in 90% ethylene glycol/10% H 2 O.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the second harmonic signal from Hg1−xCdxTe (MCT) in the presence of an anodic oxide film

Wark

McErlean

Cruickshank

et al. 2010

Journal of Electroanalytical Chemistry

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“…case of detectors passivated by CdTe in comparison to those passivated by AO. Improvement in the detector performance by CdTe passivation is on the expected lines as the AO/n-HgCdTe interface had been reported to contain large fixed positive charges, [24][25][26][27][28][29][30] leading to over accumulation of n-HgCdTe surface causing degradation in the detector performance. 31,32 The AO is grown by an electrochemical process and the oxidation reaction is reported to be strong enough to damage the HgCdTe (x ϭ 0.2) surface up to a depth of ϳ200 Å beneath the oxide-HgCdTe interface.…”

Section: Detector Performancementioning

confidence: 99%

A CdTe passivation process for long wavelength infrared HgCdTe photo-detectors

Kumar

Pal

Chaudhury

et al. 2005

J. Electron. Mater.

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Passivant-Hg 1-x Cd x Te interface has been studied for the CdTe and anodic oxide (AO) passivants. The former passivation process yields five times lower surface recombination velocity than the latter process. Temperature dependence of surface recombination velocity of the CdTe/n-HgCdTe and AO/nHgCdTe interface is analyzed. Activation energy of the surface traps for CdTe and AO-passivated wafers are estimated to be in the range of 7-10 meV. These levels are understood to be arising from Hg vacancies at the HgCdTe surface. Fixed charge density for CdTe/n-HgCdTe interface measured by CV technique is 5 ϫ 10 10 cm Ϫ2 , which is comparable to the epitaxially grown CdTe films. An order of magnitude improvement in responsivity and a factor of 4 increase in specific detectivity (D*) is achieved by CdTe passivation over AO passivation. This study has been conducted on photoconductive detectors to qualify the CdTe passivation process, with an ultimate aim to use it for the passivation of p-on-n and n-on-p HgCdTe photodiodes.

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“…Recently, we presented a generalized PC model including this effect [5] for HgCdTe PC devices. Real detectors are always having both front and rear surfaces passivated with native anodic oxide which accumulates the n-type mercury cadmium telluride (n-HgCdTe or MCT) surface due to its positive fixed surface state charge density (Q ss ) at the MCT surface [6]. The accumulation layers at the front and rear surface are sources of shunt resistances in these detectors.…”

Section: Introductionmentioning

confidence: 99%