P. Dubreuil

Feasibility study of a junction termination using deep trench isolation technique for the realization of DT-SJMOSFETs

In this work, a new design of high voltage (1200 Volts range) power superjunction MOSFET (SJMOSFET) is presented: the deep trench SJMOSFET (DT-SJMOSFET). Besides, a new junction termination, consisting in a 70 mum width and 100 mum depth trench filled by a dielectric, is proposed. Simulation results show that this junction termination exhibits the same blocking voltage capability as the base cell (central cell). In addition, the termination breakdown voltage dependence on the dielectric critical electric field (ECd) and its permittivity (epsivrd) is studied. Finally, the possibility of filling the trench termination using low dielectric polyimide such as BenzoCycloButene (BCB) is successfully approved and the Chemical Mechanical Polishing of BCB is also discussed. These experimental results represent the key steps for a future complete fabrication process of DT-SJMOSFET.

Precise Frequency Spacing in Photonic Crystal DFB Laser Arrays

We have developed integrated distributed-feedback laser arrays using photonic crystal waveguide on a membrane. They exhibit stable single-mode emission. Using both different lattice constants and a method called affine deformation of the crystal, we obtained extended control over the lasing wavelength. Laser arrays with laser-to-laser wavelength shifts as small as 0.3 nm are achieved.

Realization of vertical P/sup +/ walls through-wafer for bi-directional current and voltage power integrated devices

P/sup +/ walls through wafer can be considered as a region key in the 3D architecture of new bi-directional current and voltage power integrated devices. In this paper, we demonstrate the possibility of fabricating these P/sup +/ walls combining the deep RIE of silicon and deposit of boron doped polysilicon.

Detection of lateral spontaneous emission for VCSEL monitoring

VCSELs (Vertical Cavity Surface Emitting Lasers) are nowadays more and more exploited in optoelectronic applications, monitoring their lasing power in a compact and low cost manner becomes crucial. To collect and control the output light, an external photodetector associated with an optical microlens array can be used. Integrated solutions based on the use of a bulk or QW photodetection section added in single-or double-cavity structures have also been proposed. Here, we have investigated a simpler solution based on a standard VCSEL array. Light emitted by a VCSEL has been electrically detected by adjacent VCSELs located in the same array, using in plane optical waveguiding of spontaneous emission in the intrinsic central zone of the devices. We show that the detected photocurrent can be related to the power of the emitting VCSEL. Signal intensity has been studied as a function of VCSELs distance. This method could lead to a more efficient way to monitor VCSEL emission.

Realization of vertical P + wall through-wafer

P+ walls through wafer can be considered as key regions in the 3D architecture of new bi-directional current and voltage power integrated devices. Moreover, these P+ walls can be used as electrical vias in the design of microsystems, in order to make easier 3D packaging. In this paper, we demonstrate the possibility of fabricating these P+ walls combining the deep RIE of silicon and deposit of boron-doped polysilicon.

GaSb-based photonic crystal coupled cavity lasers above 2.3 μm

Laser diodes emitting in the mid-infrared 2-2.7 μm range are of particular interest for spectroscopic applications and especially for trace gas detection due to the presence of strong absorption bands of several species [1] of pollutants. These applications require single-frequency, wavelength tunable lasers. In this perspective, we have studied designs made of two coupled cavities (C2), coupled by an intracavity Photonic Crystal (PhC) mirror as proposed by Happ et al. [2]. The first devices of this type have recently been proposed on GaSb, emitting at 1.9 μm [4]. In this paper, we demonstrate the first coupled cavity (C2) PhC devices operating above 2.3 μm.

Effects of selective wet etching on the spectral properties of a vertical-cavity surface-emitting laser/detector

In this paper, we present results on modelling, fabrication and characterization of oxide-confined VCSELs for short-distance alternative emission and photodetection at 820 nm. In the present designed single-cavity GaAs-based device, the buried oxide layer is not only used to obtain a single mode laser beam but also to enable decoupling between a small surface emission, limited by the aperture and a large surface detection, limited by the internal diameter of the top electrodes. The selective wet etching was found to improve simultaneously the detection sensitivity and the differential quantum efficiency without damaging the active surface.

Dual-purpose single-cavity oxide-confined VCSEL photodetector

The increasing interest for high-speed, compact and low cost devices for optoelectronic applications such as bi-directional optical interconnects, optical imaging or telemetry has recently led to focus on the ability for the vertical-cavity surface-emitting lasers to be used as resonant cavity enhanced photodetectors for dual-purpose applications. Here we present results on design, fabrication and characterization of an oxide-confined 830nm top-emitting laser for self-aligned emission and photodetection. In this single-cavity GaAs-based device, submitted alternatively to forward and reverse bias, the oxide layer is not only used to obtain a single mode emission but also to enable decoupling between a small surface emission and a large surface detection. However the optical path is observed to change because of the refractive index difference between the oxidized and non-oxidized zones of the structure. This leads to a detrimental blue-shift on the wavelength of the Fabry-Perot cavity mode. In this work, we demonstrate this effect in photodetection by the means of spatially localized photocurrent and reflectance spectra measurements. These results show that the photocurrent is correctly collected in the whole device despite of the presence of an oxide layer. The results obtained on selective etching for optimisation of this dual-purpose device are presented.