Realising Si-based electrically driven light emitters in a process technology compatible with mainstream microelectronics CMOS technology is key requirement for the implementation of low-cost Si-based optoelectronics and thus one of the big challenges of semiconductor technology. This work has focused on the development of microcavity enhanced silicon LEDs (MCLEDs), including their design, fabrication, and experimental as well as theoretical analysis. As a light emitting layer the abrupt pn-junction of a Si-diode was used, which was fabricated by ion implantation of boron into n-type silicon. Such forward biased pn-junctions exhibit room-temperature EL at a wavelength of 1138 nm with a reasonably high power efficiency of 0.1% [1]. Two MCLEDs emitting light at the resonant wavelength about 1150 nm were demonstrated: a) 1 MCLED with the resonator formed by 90 nm thin metallic CoSi2 mirror at the bottom and semitranparent distributed Bragg reflector (DBR) on the top; b) 5:5 MCLED with the resonator formed by high reflecting DBR at the bottom and semitransparent top DBR. Using the appoach of the 5:5 MCLED with two DBRs the extraction efficiency is enhanced by about 65% compared to the silicon bulk pn-junction diode.

Realising Si-based electrically driven light emitters in a process technology compatible with mainstream microelectronics CMOS technology is key requirement for the implementation of low-cost Si-based optoelectronics and thus one of the big challenges of semiconductor technology. This work has focused on the development of microcavity enhanced silicon LEDs (MCLEDs), including their design, fabrication, and experimental as well as theoretical analysis. As a light emitting layer the abrupt pn-junction of a Si-diode was used, which was fabricated by ion implantation of boron into n-type silicon. Such forward biased pn-junctions exhibit room-temperature EL at a wavelength of 1138 nm with a reasonably high power efficiency of 0.1% [1]. Two MCLEDs emitting light at the resonant wavelength about 1150 nm were demonstrated: a) 1 MCLED with the resonator formed by 90 nm thin metallic CoSi2 mirror at the bottom and semitranparent distributed Bragg reflector (DBR) on the top; b) 5:5 MCLED with the resonator formed by high reflecting DBR at the bottom and semitransparent top DBR. Using the appoach of the 5:5 MCLED with two DBRs the extraction efficiency is enhanced by about 65% compared to the silicon bulk pn-junction diode.:List of Abbreviations and Symbols 1 Introduction and motivation 2 Theory 2.1 Electronic band structure of semiconductors 2.2 Light emitting diodes (LED) 2.2.1 History of LED 2.2.2 Mechanisms of light emission 2.2.3 Electrical properties of LED 2.2.4 LED e ciency 2.3 Si based light emitters 2.4 Microcavity enhanced light emitting pn-diode 2.4.1 Bragg reflectors 2.4.2 Fabry-Perot resonators 2.4.3 Optical mode density and emission enhancement in coplanar Fabry-Perot resonator 2.4.4 Design and optical properties of a Si microcavity LED 3 Preparation and characterisation methods 3.1 Preparation techniques 3.1.1 Thermal oxidation of silicon 3.1.2 Photolithography 3.1.3 Wet chemical cleaning and etching 3.1.4 Ion implantation 3.1.5 Plasma Enhanced Chemical Vapour Deposition (PECVD) of silicon nitride 3.1.6 Magnetron sputter deposition 3.2 Characterization techniques 3.2.1 Variable Angle Spectroscopic Ellipsometry (VASE) 3.2.2 Fourier Transform Infrared Spectroscopy (FTIR) 3.2.3 Microscopy 3.2.4 Electroluminescence and photoluminescence measurements 4 Experiments, results and discussion 4.1 Used substrates 4.1.1 Silicon substrates 4.1.2 Silicon-On-Insulator (SOI) substrates 4.2 Fabrication and characterization of distributed Bragg reflectors 4.2.1 Deposition and characterization of SiO2 4.2.2 Deposition of Si 4.2.3 Distributed Bragg Reflectors (DBR) 4.2.4 Conclusions 4.3 Design of Si pn-junction LED 4.4 Resonant microcavity LED with CoSi2 bottom mirror 4.4.1 Device preparation 4.4.2 Electrical Si diode characteristics 4.4.3 EL spectra 4.4.4 Conclusions 4.5 Si based microcavity LED with two DBRs 4.5.1 Test device 4.5.2 Device fabrication 4.5.3 LED on SOI versus MCLED 4.5.4 Conclusions 5 Summary and outlook 5.1 Summary 5.2 Outlook A Appendix A.1 The parametrization of optical constants A.1.1 Kramers-Kronig relations A.1.2 Forouhi-Bloomer dispersion formula A.1.3 Tauc-Lorentz dispersion formula A.1.4 Sellmeier dispersion formula A.2 Wafer holder List of publications Acknowledgements Declaration / Versicherung