The goal of this experimental research program is a fundamental understanding of the hydrogen impurity and its properties in semiconductor host materials that are important in electronics technology. Vibrational spectroscopy of the light hydrogen atom has proved to be a powerful probe of the microscopic structure and properties of hydrogen-containing defects and is the principal method used in this project. Recent advances make the following experiments attractive: (i) Hydrogen has been found to increase the band gap of dilute III-N-V alloys. Vibrational spectroscopy provides information about the structures of the defects causing this effect and the number of hydrogen atoms they contain. (ii) Hydrogen forms interstitial molecules in Si whose rotational-vibrational properties have recently been deciphered. Infrared spectroscopy is used to probe the ortho-para transition of the interstitial hydrogen molecule. (iii) H has been found to have a strong effect on the conductivity of semiconducting oxides like ZnO. Vibrational spectroscopy of H implanted into ZnO at cryogenic temperature investigates the properties of the fundamental isolated hydrogen defect. Graduate and undergraduate students conduct the experiments on impurities in semiconductors that are the focus of this research program. Students learn about the physics of semiconductors, the optical properties of materials, and crystal defects. This experience provides an excellent foundation for careers in science and engineering.
An understanding of the hydrogen impurity in semiconductors is vital in electronics technology. Hydrogen is introduced easily into semiconductors, either intentionally or unintentionally. Once present, hydrogen modifies the electrical properties of semiconductor materials and the behavior of electronic devices. Experimental studies of the microscopic structures and fundamental properties of defect "molecules" in semiconductors that contain hydrogen are the focus of this research program. The semiconductor materials that are of interest include Si, which is important for integrated circuits and solar cells, and compound semiconductors, which are important for light-emitting devices. We extend our research to relevant areas of semiconductor technology. For example, a method to detect the small concentration of hydrogen introduced into Si by methods used by industry to improve the efficiencies of solar cells has been developed and used to study manufacturing processes. This research program on hydrogen in semiconductors provides an excellent opportunity for undergraduate and graduate students to make important contributions to problems in physics that have an impact on electronics technology, often in collaboration with leading scientists in the U.S. and abroad.
