A. Splett

Integrated optics in silicon and SiGe-heterostructures

This paper reviews various techniques and ideas in the field of integrated optics in silicon, mainly focused on silicon in conjunction with germanium. We will discuss different approaches for waveguides, passive and active components in silicon as well as recent developments in the fabrication and performance of such components. For waveguides in silicon, the characteristics such as losses and spot-sizes are given, showing that silicon could be an attractive candidate for integrated optical devices.

Integration of waveguides and photodetectors in SiGe for 1.3 /spl mu/m operation

The integration of single-mode rib waveguides and photodetectors in silicon using MBE-grown SiGe-layers is reported. Short photodetectors exhibit dark currents below 200 nA at 7 V reverse bias. For the fiber-waveguide-detector coupling an overall quantum efficiency of 11% has been achieved at 7 V reverse bias for /spl lambda/=1.3 /spl mu/m. The maximum bandwidth is 2 GHz.<<ETX>>

Room‐temperature electroluminescence from Si/Ge/Si1−xGex quantum‐well diodes grown by molecular‐beam epitaxy

Tunable room‐temperature electroluminescence, photocurrent, and photoluminescence in the near infrared (λ∼1.3 μm) has been observed from Ge/Si/Ge/Si1−xGex quantum‐well (QW) diodes grown by molecular‐beam epitaxy. The QWs are grown on a p+‐doped 〈100〉‐Si substrate and consist of two thin Ge wells separated by a thicker Si middle layer, and the whole structure is embedded by two Si0.85Ge0.15 alloy layers. Our theoretical analysis of the data suggests that the strength of the spectra is linked to states localized at the interface.

Low loss single-mode optical waveguides with large cross-section in standard epitaxial silicon

Single-mode waveguides, well matched to the fiber spot size, have been fabricated by chemical etching of standard epitaxial silicon. Analytical estimations for the waveguide attenuation are given. Measured waveguide losses below 1.5 dB/cm have been obtained at both wavelengths, /spl lambda/=1.3 /spl mu/m and /spl lambda/=1.55 /spl mu/m.<<ETX>>

Germanium-diffused waveguides in silicon for lambda =1.3 mu m and lambda =1.55 mu m with losses below 0.5 dB/cm

The authors present a simple technique for the fabrication of integrated optical channel waveguides that are prepared by indiffusion of an E-beam evaporated amorphous alloy of germanium and silicon into commercially available silicon with low dopant concentration, using only simple technological processes such as standard lithography, PVD, and diffusion. The waveguides are polarization independent and have waveguide losses as low as 0.3 dB/cm at wavelengths of lambda =1.3 mu m and lambda =1.55 mu m. The spot sizes are well suited for low-loss single-mode fiber device coupling, being on the order of a few microns in both horizontal and vertical directions.<<ETX>>

Integrated optoelectronic waveguide detectors in SiGe for optical communications

The monolithic integration of a SiGe-optical waveguide with a detector based on SiGe- absorbing layers is presented. A maximum internal quantum efficiency of (eta) equals 40% has been measured at (lambda) equals 1.3 micrometers , which corresponds to an external efficiency of (eta) equals 11%. This device is suitable for 2.5 GBit/s data transmission, the performance is limited by the RC time constant due to a capacitance of C equals 1.7 pF.

Series-Expansion-Beam-Propagation-Method for the vector wave equation

Recently, there has been much interest in solving the vector wave equation by beam-propagation-method-type algorithms [1][2][3][4]. Most of the proposed algorithms are based on scalar propagation algorithms which suffer from accuracy limitations for large propagation steps. Implicite formulations involving a Crank-Nicholson scheme[3] or similar methods [4] become more complex in a two-dimensional cross-section. In this work it is shown, that a recently proposed beam propagation method[5] using a rigorous Taylor-series expansion can be used to solve the vector wave equation with high accuracy and without major changes in calculation effort.

Low loss integrated-optical rib-waveguides in SOI

Low-loss integrated-optical rib-waveguides in SOI (silicon-on-insulator) were fabricated and characterized. Using

Integrated Optics in Silicon

A technique for fabricating low loss channel waveguides in silicon is reported. The waveguides are obtained by an indiffusion of germanium diffused from a SiGe-alloy. The fabrication process is described in detail and typical fabrication parameters are given. The waveguides are characterized optically by loss- and spot-size-measurements, both, theoretically and experimentally.

Absorption and emission characteristics of mesa and ridge waveguide diodes made from strain adjusted SImGEn superlattice and SI/GE quantum well layers grown by MBE

We have fabricated mesa and ridge waveguide diodes from Si/Ge quantum well (QW) and short-period superlattice samples deposited by MBE on a (100) Si substrate. We have grown Si/Ge/Si1-xGex QW samples consisting of thin Ge wells where 20 MLs of Si are embedded in-between and followed by a SiGe layer elastically strained on a Si substrate as well as symmetrically strained on a strain symmetrizing buffer layer. We have also grown SimGen short-period, strained layer superlattices consisting of N periods of (m + n) monolayers per period which are deposited on a strain adjusting buffer layer. The edge emitting ridge waveguide diodes fabricated from this material with standard semiconductor processing techniques were polished on the <110> side faces and etched to a height of roughly 1.0 micrometers with lateral dimensions of roughly 100 micrometers width X 3 mm length. Also circular mesa diodes were fabricated with the same height and varying diameters from 100 micrometers to 800 micrometers and were provided with a metal ring contact on top defining the illumination window. Photocurrent and electroluminescence signals at h(nu) approximately 0.8 eV were detected at room temperature from QW samples. The emission characteristics as a function of strain and composition of the SLS and QW layers are discussed.