Papers by Author: R. Jones

Abstract: The electronic properties and structure of a complex incorporating a self-interstitial (I) and two oxygen atoms are presented by a combination of deep level transient spectroscopy (DLTS), infrared absorption spectroscopy and ab-initio modeling studies. It is argued that the IO2 complex in Si can exist in four charge states (IO− 2 , IO02 , IO+ 2 , and IO++ 2 ). The first and the second donor levels of the IO2 complex show an inverted location order in the gap, leading to a E(0/ + +) occupancy level at Ev + 0.255 eV. Activation energies for hole emission, transformation barriers between different structures, and positions of LVM lines for different configurations and charge states have been determined. These observables were calculated by density-functional calculations, which show that they are accounted for if we consider at least two charge-dependent defect structures.

Abstract: We report on a combined experimental and theoretical study of the metastable form of the vacancy-dioxygen defect in Si labeled VO∗ 2. Important new experimental observations are the detection of mixed local vibrational modes of VO∗ 2 in 16O,18O co-doped samples, the determination of the position of LVM bands for the negatively charged defect, and an assignment of an acceptor level at about Ec − 0.05 eV. Defect energetics, electrical levels and LVM frequencies of the VO∗ 2 complex are also investigated by ab-initio density-functional modeling.We find it to be a bistable defect which accounts well for the experimental data. The metastable form produces an acceptor state at 0.05 eV below Ec, and can be thought of as a VO defect perturbed by interstitial oxygen.

Abstract: We report on the energetics, electrical and optical activity of small self-interstitial (I3 and I4) clusters in Si, found from ab-initio density-functional modeling studies. I4 possesses nine local vibrational modes above the Raman edge, which account for up to three dipole-allowed vibronic transitions observed in recent experiments associated with the X-photoluminescent line. Another prominent photoluminescent line (known as the W-line) that shows a trigonal stress-induced splitting pattern, has been previously assigned to I3. Our analysis of the LVMs of a metastable form of I3 support this assignment.

Abstract: 90 Shockley partial dislocations in GaN are investigated by first-principles calculations. This work is focussed on the electrical properties of dislocation cores, and on investigating the electrical fields around these defects. The band structure analysis shows that both the  and  core partials possess a midgap state. The -core dislocations give rise to a donor level Ev +0:87 eV that might explain the absorption peak at 2.4 eV revealed by energy loss spectroscopy measurements. The acceptor level Ev + 1:11 eV localized at the -core dislocations might contribute to the yellow luminescence. These dislocations experience a substantial charge polarization along the [0001] growth axis. In addition, we show that these dislocations tend to charge in a high stress field.