Comparative studies on structural, compositional, morphological and optical properties of ZnSe and ZnSSe single crystals grown by CVT method

Perumal Kannappan ,  Ramasamy Dhanasekaran 

Crystal Growth Centre, Anna University, Chennai 600 025, India

Abstract

Corresponding Author Email: rdcgc@yahoo.com ; Tel: +91-44 2235 8317

  The ZnSe and ZnSSe single crystals are wide and direct band gap II-VI compound semiconductors. These single crystals are of immense importance in visible optoelectronic applications such as light emitting diodes (LEDs), laser diodes (LDs) and many electronic devices. The ZnSxSe1-x is a solid solution of two binary compound semiconductors ZnS (3.67 eV) and ZnSe (2.67 eV) where the band gap energy changes continuously with the composition of x. The ZnSe and ZnSSe single crystals were grown by chemical vapour transport (CVT) with iodine as a transporting agent. The source and growth temperatures of the reactor are 850˚C and 900˚C respectively using the two zone horizontal resistive heating furnace. The growth period was 15 days for ZnSe and 10 days for ZnSSe single crystals. The maximum dimension of the grown crystal is 9 x 7 x 5 mm3. The grown crystals were characterized. The XRD pattern shows the peaks corresponding to (111), (200) and (311) planes which confirm the formation of crystalline phase. ZnSe and ZnSSe crystals belong to cubic zinc-blende structure. The composition of the grown ZnSe crystal were studied by EDAX analysis as Zn (52.5%) and Se (47.5%) and ZnSSe crystal has Zn (43.56%), S (29.86%) and Se (26.58%). The surface morphology of ZnSe and ZnSSe single crystals shows the parallel step growth pattern in the order of micrometer regions. The optical absorption study reveals the cut off wavelength as 483 nm (2.57 eV) for ZnSe and the 441 nm (2.81 eV) for ZnSSe single crystals. The photoluminescence show the band edge emission 440 nm and defect level emission at 590 nm. FT-Raman study shows the lattice vibrations of LO and TO modes which confirm the tetrahedral site symmetry of ZnSe and ZnSSe single crystals.

Key words: Crystal growth, Structural, Compositional, Surface morphological, Optical proeprties

 

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Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 4, by Perumal Kannappan
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-11 14:51
Revised:   2013-07-26 12:32