Chemical vapor transport of chalcopyrite semiconductors: CuGaS2 and AgGaS2

• Published in: Journal of crystal growth Vol. 401; pp. 708 - 711
• Main Authors: Lauck, R., Cardona, M., Kremer, R.K., Siegle, G., Bhosale, J.S., Ramdas, A.K., Alawadhi, H., Miotkowski, I., Romero, A.H., Muñoz, A., Burger, A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-09-2014; Elsevier
• Subjects: A1. Characterization; A1. Etching; A1. Purification; A2. Growth from vapor; B1. Sulfides; B2. Semiconducting ternary compounds; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from vapor; Materials science; Methods of crystal growth; physics of crystal growth; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; B1. Sulfides; A1. Etching; A1. Characterization; A1. Purification; A2. Growth from vapor; B2. Semiconducting ternary compounds; Acoustical phonons; Etching; Sulfides; Blood platelets; Optical properties; Copper; Temperature dependence; Vacuum annealing; Purification; Semiconductor materials; Ternary compounds; Sublimation; Reflectivity; Growth from vapor; Optical phonons; Chalcopyrite; Chemical transport; Growth mechanism; Crystal faces; Thermodynamic properties
• DOI: 10.1016/j.jcrysgro.2014.01.071
• EISSN: 1873-5002
• ISSN: 0022-0248

Crystals of CuGaS2 and AgGaS2 with different isotopic compositions have been grown by chemical vapor transport (CVT) using iodine as the transport agent. Before performing the CVT growth, sulfur and copper were purified by sublimation and etching, respectively. 109Ag and the etched 71Ga isotopes were purified from oxides by vacuum annealing. Transparent yellow orange crystals of CuGaS2 and greenish yellow crystals of AgGaS2 were obtained in the shape of platelets, chunks, rods and needles in sizes of up to 8mm (CuGaS2) and 30mm (AgGaS2).
These crystals were used to study their electronic, vibrational and thermodynamic properties. Higher excitonic states (n=2,3) were observed at low temperatures with wavelength-modulated reflectivity spectroscopy, thus proving an excellent surface and crystal quality. In addition, the experimentally determined non-monotonic temperature dependence of the excitonic energies can be well fitted by using two Bose–Einstein oscillators and their statistical factors, corresponding to characteristic acoustic and optical phonon frequencies. Isotopic shift of excitonic energies has also been successfully observed in these crystals.
•We have grown crystals of CuGaS2 and AgGaS2 by chemical vapor transport with iodine.•Wavelength-modulated reflectivity provides exciton spectra in high resolution.•Higher excitonic states indicate an excellent crystal quality.•Exciton energies show anomalous non-monotonic temperature dependence.•Isotopic shift of excitonic energies has been measured.