The lateral wet-etching kinetics of an Al0.8Ga0.2As sacrificial layer, a typical configuration for optoelectronic devices, has been investigated in detail. Expanding the one-dimensional Si and AlAs oxidation modes to the Al0.8Ga0.2As sacrificial layer etching process, compact analytical formulas were obtained for the time evolution of the etch front and for the etch rate. Through both experiment and theoretical calculations, the lateral etching process parameters, A, B, and B∕A, have been obtained for the different temperatures and etchant volume ratios. The etch rate is found to remain almost constant for a large range of etch length. However, when the etch temperature increases, a rapid increase in this rate is predicted. Activation energies for the process parameters, EA∼0.1eV and EB∼0.5eV, have also been obtained for the etchant volume ratio of 3:1 and the sacrificial layer thickness is 800nm.

In this paper, according to the relationships of the etch-rate with the FWs from 2μm to 100μm and of the etch-rate changes with etch-time for a particular FW, obtained by our experiments, a possible etching process model were proposed. When the etch-time was relatively short, it was the reaction limited process. With the etch-time going on, the fresh reactive gas was difficult to get through the etching trench to the fresh reaction interface, the etch-rate decreased, which was called the residual removing limited process. Our mathematic fitting results proved the above etching model and pointed that for the reaction limited process, the etch depth linearly increase with the etch time. While it got into the residual removing limited process, the etch-rate decreased.