II-VI Semiconductor Materials, Devices, and Applications Tony Stein EE 4611

Overview List of II-VI Semiconductor Materials General Properties Applications of Each Compound Overview/Conclusion References Key Points

Common II-VI Compounds Zinc Oxide Zinc Sulfide Zinc Selenide Zinc Telluride Cadmium Sulfide Cadmium Selenide Cadmium Telluride http://www.science-kick.com/solar-cell-type/ii-vi-materials-based-junction-solar-cells

Advantages Wide Band Gap ranging from 1.5 eV to 3.54 eV Compare to Si Band Gap of 1.1 eV Wide Band Gap allows devices to operate at much higher voltages, frequencies and temperatures Higher Breakdown Voltage = High Power & Frequency Applications Higher Doping Concentration = Thinner Device Layers Higher Electron Mobility = Faster Operation

Cadmium Sulfide (CdS) Conductivity increases when exposed to light Leading to use as a photoresistor It forms the core component of a solar cell http://www.electronicshub.org/light-sensors/

Cadmium Sulfide (CdS) Cont. Piezoelectric and Pyroelectric capabilities CdS crystal can act as a solid state laser Electroluminescence capabilities fabtolab.com https://upload.wikimedia.org/wikipedia/commons/6/61/NightLight.jpg

http://www. creationscience http://www.creationscience.com/onlinebook/webpictures/radioactivity-piezoelectric_effect.jpg

Cadmium Selenide (CdSe) Applications: Solar Cells, LEDs, Biomedical Imaging Much of the current research on cadmium selenide is focused on its nanoparticles

Cadmium Selenide (CdSe) Cont. One type of CdSe nanoparticle is a CdSe quantum dot Quantum dots are small semiconductor particles Will emit light of specific frequencies if electricity or light is applied to them These frequencies can be precisely tuned by changing the dots size and shape, giving rise to many applications.

Potential applications include transistors, solar cells, LEDs, diode lasers http://mix.msfc.nasa.gov/abstracts.php?p=3906

http://ffden-2. phys. uaf. edu/631fall2008_web http://ffden-2.phys.uaf.edu/631fall2008_web.dir/wallace_webpage/spectrum.png

Cadmium Telluride (CdTe) CdTe can be alloyed with mercury to make an infrared detector material (HgCdTe) CdTe doped with chlorine is used as a radiation detector for x-rays, gamma rays, beta particles and alpha particles Used to make Thin Film solar cells http://www.nrel.gov/data/pix/Jpegs/14726.jpg

Cheaper but less efficient than conventional photovoltaic technology. Film thickness varies from a few nanometers to tens of micrometers - Much thinner than 1st generation PV -(200µm) Cheaper but less efficient than conventional photovoltaic technology. Faster degradation compared to conventional PV http://www.nrel.gov/data/pix/Jpegs/14726.jpg

Zinc Oxide (ZnO) Transparent thin-film Transistors Photodetectors LEDs Laser Diodes

Zinc Sulfide (ZnS) Zinc Sulfide can be transparent and used as a window for visible optics and infrared optics Used in Electroluminescent Panels https://commons.wikimedia.org/w/index.php?curid=43438017

Zinc Selenide (ZnSe) LEDs, Diode Lasers X-ray and gamma ray detectors Luminescent Infrared Optical Material visiblediodelasers.com

Zinc Telluride (ZnTe) Optoelectronics LEDs Laser Diodes Solar Cells

Summary II-VI semiconductor materials are becoming increasingly important in the semiconductor industry. These compounds are integrating themselves into modern electronics and replacing conventional silicon in certain applications. While it’s impossible to determine just how large of an effect these materials will have and how long-lived they will be, high power electronics, the military, and the medical industry are already benefiting from them.

References D. Lincot, Gary Hodes Chemical Solution Deposition of Semiconducting and Non-Metallic Films: Proceedings of the International Symposium The Electrochemical Society, 2006 ISBN 1-56677- 433-0 H. Zhao et al, "The effect of impurities on the doping and VOC of CdTe/CdS thin film solar cells", Thin Solid Films, Vol. 517, No. 7 (2009) pp. 2365-2369, [1] doi:10.1016/j.tsf.2008.11.041 Minkus, Wilfred (1965). "Temperature Dependence of the Pyroelectric Effect in Cadmium Sulfide". Physical Review. 138 (4A): A1277. Bibcode:1965PhRv..138.1277M. doi:10.1103/PhysRev.138.A1277. Robel, I.; Subramanian, V.; Kuno, M.; Kamat, P.V. (2006). "Quantum Dot Solar Cells. Harvesting Light Energy with CdSe Nanocrystals Molecularly Linked to Mesoscopic TiO2 Films". J. Am. Chem. Soc. 128: 2385–2393. doi:10.1021/ja056494n.

References Bakin, A.; et al. (2010). "ZnO – GaN Hybrid Heterostructures as Potential Cost Efficient LED Technology". IEEE (Invited Paper for a special volume), Proceedings of the IEEE. 98 (7): 1281– 1287. doi:10.1109/JPROC.2009.2037444. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 12.80. ISBN 1439855110. Kittel, C. (1976) Introduction to Solid State Physics, 5th edition, p. 28. Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12- 352651-5 Efros, Al. L.; Rosen, M. (2000). "The electronic structure of semiconductor nanocrystals". Annual Review of Materials Science. 30: 475–521. Bibcode:2000AnRMS..30..475E. doi:10.1146/annurev.matsci.30.1.475.

References Chalcogenide Photovoltaics: Physics, Technologies, and Thin Film Devices by Scheer and Schock, page 6. Link (subscription required). "Nowadays, CdTe modules are produced on the GWp/year level and currently are the cost leader in the photovoltaic industry."

Key Topics Common Compounds of II-VI Semiconductors Advantages of Wide Band Gap semiconductors Quantum Dots will emit light of specific frequencies if electricity or light is applied to them How does a piezoelectric transducer work? Thin film Solar cells are cheaper but less efficient than silicon solar cells