J. Wong-Leung

The precipitation of Fe at the Si–SiO2 interface

We report on the precipitation kinetics of Fe contamination at Si–SiO2 interfaces during dry oxidation at 900 °C. Transmission electron microscopy (TEM) and atomic force microscopy are used to monitor the interface roughness and precipitate density for oxides formed in the presence of both bulk and surface contamination of the Si. We show that the precipitating phase is β-FeSi2, the equilibrium Fe–Si phase (rather than α-FeSi2 or an iron silicate or iron oxide). The interface precipitate density is proportional to the surface Fe, and differs in float-zone and Czochralski Si. These precipitates correlate with the presence of sharp asperities at the interface. Detectable Fe precipitation is measured in TEM for contamination levels down to 1×1013 cm−2. In contrast, bulk contamination to above the solid solubility does not generate observable precipitation at the oxide interface.

Dynamic annealing in ion implanted SiC: Flux versus temperature dependence

Partial financial support for this work was received from the Swedish Foundation for Strategic Research ~SSF!, the Swedish Foundation for International Cooperation in Research and Higher Education ~STINT!, the Norwegian Research Council ~NFR!, and the Nordic Academy for Education and Research Training ~NorFA!. One of the authors ~J.W.L.! acknowledges the Australian Research Council for funding under the fellowship program.

Effect of crystal orientation on the implant profile of 60 keV Al into 4H-SiC crystals

The authors acknowledge the STINT ~Swedish Foundation for international cooperation in research and higher education! program and Australian Research Council for support under the Discovery grant and fellowship program.

Effect of implant temperature on secondary defects created by MeV Sn implantation in silicon

One of the authors (J.W-L.) would like to acknowledge the Australian Research Council for financial support under the ARC fellowship program.

Selective Intermixing of InGaAs/GaAs Quantum Dot Infrared Photodetectors

Quantum dot infrared photodetectors have generated significant interest in recent years. They have the potential to outperform quantum well detectors in terms of normal-incidence responsivity and higher operating temperatures. Here, an InGaAs/GaAs dots-in-a-well detector grown by metal-organic chemical vapor deposition is spectrally tuned by rapid thermal annealing under dielectric layers. Four films are considered: SiO2 deposited by both plasma-enhanced chemical vapor deposition and sputter deposition, as well as TiO2 deposited by electron-beam evaporation and sputter deposition. The devices fabricated after these treatments are compared with an uncapped but annealed reference, and also with an as-grown device. The photoresponse peak in the latter occurs at 7.1 μm, whereas the peak responses of the annealed devices range from 7.4 to 11.0 μm. The films themselves were characterized and their properties related to the photoluminescence and spectral photoresponse of each detector. Peak responsivity, specific detectivity, and dark current were also measured for each device to compare their performance.

Ion Implantation Processing and Related Effects in SiC

A brief survey is given of some recent progress regarding ion implantation processing and related effects in 4H- and 6H-SiC. Four topics are discussed; an empirical ion range distribution simulator, dynamic defect annealing during implantation, formation of highly p+-doped layers, and deactivation of N donors by ion-induced defects.

Identification by photoluminescence and positron annihilation of vacancy and interstitial intrinsic defects in ion-implanted silicon

This work was supported by EPSRC Grant No. GR/R 10820/01 and by the EU Coordination Action program CADRES. One of the authors J.W.L. thanks the Australian Research Council for a fellowship.

Self-assembled Au nanoparticles in SiO2 by ion implantation and wet oxidation

Implantation, annealing, and oxidation processes have been used to form Au nanoparticles with a narrow size and depth distribution in a SiO2 layer. Different approaches have been attempted: in particular, the gettering of Au to fill preformed nanocavities (obtained by H-implantation and annealing) and thus overcome the broad particle size distribution that is normally associated with nanoparticles formed by implantation and annealing. The results suggest that nanocavities cannot be directly formed in SiO2 by H-implantation and a subsequent annealing due partly to the high mobility of H atoms in SiO2. However, cavities formed in Si are useful in obtaining a narrow size and depth distribution of Au precipitates: the Si substrate can then be oxidized to form Au nanoparticles in SiO2. Sequential wet oxidations of Si samples containing Au nanoparticles have revealed several interesting phenomena, namely, segregation of Au particles at a growing oxide interface, Au-enhanced oxidation, dissolution and reprecipit...

Asymmetric design of semiconductor laser diodes: thin p-clad and low divergence InGaAs/AlGaAs/GaAs devices

The asymmetric design of a semiconductor laser structure presented in this paper is based on the extension of the near field in the vertical direction (growth direction) preferentially on the n-side of the structure. P-type layers show lower mobility and higher optical losses than n-type layers. Thus the series resistance of the device and the internal losses would benefit from this approach. The vertical spot size is 0.8 /spl mu/m, making the structures also suitable for high power operation. We give the refractive index profile and optical field distribution in the asymmetric structures.

Strain relaxation in rapid thermally annealed InAs/GaAs quantum dot infrared photodetectors

In this paper the effect of rapid thermal annealing (RTA) on a 30 stacked InAs/GaAs, molecular beam epitaxially grown quantum dot infrared detector (QDIP) device is studied. Temperatures in the range of 700 - 900/spl deg/C for 60 s, typical of ion implantation induced interdiffusion, are used. Double crystal X-ray diffraction (DCXRD), photoluminescence (PL), cross sectional transmission electron microscopy (XTEM) and device electrical characteristics were used to monitor changes due to RTA. The QDIP devices had good PL signal which improved upon annealing. However the device performance after RTA was poor and DCXRD and XTEM results clearly indicate that strain relaxation is occurring. The role of strain relaxation on optical and electrical properties has been discussed.