Second harmonic generation in the characterisation of surface effects in epitaxial CdxHg1-xTe (CMT) <111> layers

Berlouis, Leonard and Wark, A. and Cruickshank, F.R. and Antoine, R. and Galletto, P. and Brevet, Pierre-Francois and Girault, H.H. and Gupta, S.C. and Chavada, F.R. and Kumar, S. and Garg, A.K. (1998) Second harmonic generation in the characterisation of surface effects in epitaxial CdxHg1-xTe (CMT) <111> layers. Semiconductor Science and Technology, 13 (10). pp. 1117-1122. ISSN 0268-1242 (https://doi.org/10.1088/0268-1242/13/10/011)

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Abstract

Second-harmonic (SH) rotational anisotropy measurements performed on epitaxial Cdx Hg1−x Te (CMT) layers grown on CdTe h111i B substrate exhibits an interference in the SH signal originating from the bulk and from the CMT surfaces. The threefold symmetry of the epilayer was shown to be sensitive to the nature of adsorbed species at the surface when in contact with an electrolyte solution despite the strong SH generation in the bulk of the layer. The modification of the SH response from a non-centrosymmetric semiconducting material to such an extent is unusual since bulk SH generation is considered as the dominant contributor in these instances. The case of CMT is, however, rather specific in that the observed SH signal originates from, at most, only the top 40 nm of the CMT epilayer. This important difference means that surface modification by means of electron donating or withdrawing groups will play a large role in the observed SHG signal.