Micro-PL characterization of oxide-confined GaAs VCSEL operating at 850 nm

International audienc

Degree of Polarization of Cathodoluminescence from a GaAs Facet in the Vicinity of an SiN Stripe

International audienceMeasurements of the cathodoluminescence (CL) and the degree of polarization (DOP) of (CL) from the facet of a GaAs substrate and in the vicinity of a SiN stripe are reported and analyzed. The deformation induced by the SiN stripe is estimated by fitting the measured DOP to 3D finite element method (FEM) simulations. The deformation is found to be more complex than an initial condition of biaxial stress in the SiN. A ratio of fit coefficients suggests that the dependence of DOP on strain is described by equations presented in Appl. Opt. 59, 5506-5520 (2020). These equations give a DOP that is either proportional to a weighted difference of the principal components of strain in the measurement plane, or proportional to the shear strain in the measurement plane, depending on the chosen orientation of the measurement axes

Mapping of mechanical strain by DOP of oxide-confined GaAs based VCSEL operating at 850 nm

International audienc

DOP characterization of oxide-confined GaAs based VCSEL operating at 850 nm

International audienc

Mechanical strain mapping of GaAs based VCSELs

International audienceWe report an investigation of the strain field in mesa structures for oxide-confined vertical-cavity surface-emitting lasers (VCSELs) using the polarization-resolved micro-photoluminescence (PL) measurement of the degree of polarization (DOP) at room temperature. The DOP of the PL is correlated with the spatial distribution of the embedded anisotropic strain in a VCSEL structure. Measurements normal to (100) surfaces of the samples and from (110) cross-sectional planes were performed. The effect of two processes required in the fabrication of GaAs-based VCSELs was studied: the plasma etching of the P-doped distributed Bragg reflector and the wet oxidation process used to control current flow and lateral optical confinement. The DOP method allows very sensitive measurements of the mechanical strain (on the order of 10 - 5) accumulated in VCSEL devices even during different steps of the fabrication process

Optical Characterizations of VCSEL for Emission at 850 nm with Al Oxide Confinement Layers

International audienceIn-plane micro-photoluminescence (mu-PL) and micro-reflectivity measurements have been performed at room temperature by optical excitation perpendicular to the surface of two different structures a complete vertical surface-emitting laser (VCSEL) structure and a VCSEL without the upper p-type distributed Bragg reflector (P-DBR). The two structures were both laterally oxidized and measurements were made on the top of oxidized and unoxidized regions. We show that, since the photoluminescence (PL) spectra consist of the cumulative effect of InGaAs/AlGaAs multi-quantum wells (MQWs) luminescence and interferences in the DBR, the presence or not of the P-DBR and oxide layers can significantly modify the spectrum. mu-PL mapping performed on full VCSEL structures clearly shows oxidized and unoxidized regions that are not resolved with visible light optical microscopy. Finally, preliminary measurements of the degree of polarization (DOP) of the PL have been made on a complete VCSEL structure before and after an oxidation process. We obtain an image of DOP measured by polarization-resolved mu-PL. These measurements allow us to evaluate the main components of strain

Micro-PL and DOP characterization of Vertical Cavity Surface Emitting Lasers (VCSEL) for emission at 850 nm with Al oxide confinement layers

International audienc

Chemical imaging of oxide confinement layers in GaAs/AlxGa1−xAs VCSELs

International audienceThe authors have studied the lateral oxidation of Al x Ga 1−x As layers buried in vertical-cavity surface-emitting lasers using cross-sectional scanning transmission electron microscopy coupled with electron energy loss spectroscopy. Chemical maps and composition profiles of the oxidized AlO x layers have been produced. The sensitivity is such that trace compositions of a few % As and Ga can be detected in the AlO x with a spatial resolution of a few nanometers on the recorded chemical maps. To demonstrate the performance of the mapping technique, we compare results from an area in the vertical-cavity surface-emitting laser (VCSEL) which is pure Al x Ga 1−x As to an oxidized area. These measurements are performed on a thin sample prepared by the focused ion beam technique within an actual VCSEL, which makes the mapping technique applicable for degradation investigations in devices at different stages of their lifetime. More generally, this measurement method is effective for detailed evaluation of AlO x layers and their fabrication process

Investigation of processing-induced defects in GaAs based vertical cavity surface emitting lasers with Al oxide confinement layers

International audienc

Investigation of processing-induced defects in GaAs based vertical cavity surface emitting lasers with Al oxide confinement layers

International audienc