Oxidation kinetics of AlAs and (AlGa)As layers in GaAs-based diode laser structures: comparative analysis of available experimental data

Abstract

An understanding of the kinetics of the steam oxidation of AlAs and (AlGa)As layers is crucial to maintain good control of the process of manufacturing modern GaAs-based diode microresonator vertical-cavity surface-emitting lasers (VCSELs). Mathematically, the process has been described in our previous publications. Our theoretical equations contain, however, a few adjustable parameters, which should be found experimentally. Therefore, in this paper, an extensive analysis of existing experimental results (including ours) is performed. It enables us to extract the physical parameters describing oxidation kinetics for the AlAs and (AlGa)As oxidation process. While some scattering in the parameters is found from measurements reported by different groups, the same general trends are observed. These results support our physical understanding of the oxidation process. Nevertheless, the oxidation process still needs some experimental investigations to establish all conditions influencing its kinetics and to enable reproducible oxidation results obtained under assumed identical technological conditions. It has been confirmed that currently theoretical modelling cannot offer a reasonable a priori control of the oxidation process without a careful calibration of a given oxidation set-up and procedure. However, the simulation may enable determination of safe limits of the process, especially important in the fabrication of small-size microresonator VCSELs.

Numerical Self-Consistent Analysis of VCSELs

“…Since the kinetics of the oxidation is strongly dependent on temperature but also on compositions and thicknesses of oxidized (AlGa)As layers [32], it is possible that apertures of different diameters may be produced in one oxidation process.…”

“…In the SCH active region, both the carrier confinement in the thin active region and the field confinement within the wider cavity are produced independently by two (inner and outer) heterojunction pairs. By analogy, the proposed VCSEL structure shown in Figure 12 is able to independently create an active-region current-density profile and a radial optical index guiding with the aid of two different oxide apertures is called the separate-confinementoxidation (SCO) structure [32] (Figure 11).…”

VCSEL structures used to suppress higher-order transverse modes

“…However, small−aperture devices exhibit higher, both thermal and electrical resis− tances, which are followed by higher active−region tempera− ture increases leading to shorter VCSEL expected lifetime and, additionally, which limit VCSEL modulation band− width and its high−speed performance [13]. Besides, techno− logy used to obtain in a control way such small oxide aper− tures may be quite difficult because of an increasing radial oxidation rate with a decrease in a diameter of an oxide aperture [14]. Nevertheless, in applications, for which the above disadvantages are not critical, small−aperture VCSELs may be the simplest and the best solution.…”

The effect of oxide aperture diameter on the electrical characteristics of the GaN-based vertical cavity surface emitting laser

“…Selective oxidation is a widely used technique in the AlAs/GaAs system [12] for successful current confinement schemes in GaAs-based VCSELs [13]. Dorsaz et al reported a procedure allowing for selective anodic oxidation of lattice-matched AlInN layers and its application to the fabrication of light-emitting diodes (LEDs) [18].…”