Evaluation of induced damage by CH 4/H 2 reactive ion etching on InP: n++

Abstract

Current optoelectronic devices extensively use dry etching for their fabrication, in particular, reactive ion etching (RIE) is the most used technique. Unfortunately, dry etching induces a damaged layer on the etched surfaces that can negatively influence the electro-optical performance of the devices in terms of specs and reliability. In this work we evaluate the thickness of the surface damaged layer induced by CH 4/H 2 RIE on InP using a technique based on the comparison of the conductance of the material before and after the RIE. The method can be used to optimise the RIE conditions in order to minimise the extension of the surface damaged layer. To perform the conductance measurements, transmission line model and Hall effect were used. Two different etching conditions have been considered. The first is typical for low etch rate (ER) (DC bias=−315 V), for example, used in grating formation for a DFB laser. The second for high ER (DC bias=−650 V), for example used in mesa etching for several kinds of buried lasers. The experimental results gave damaged thicknesses of 130 and 340 Å, respectively, for low and high ER conditions. This thin layer can be easily removed by annealing and with a very short wet etching to give high performances devices (27th European Conference on Optical Communication ECOC‘01, Amsterdam).