We present a Nobel modified technique of in situ etching with tertiarybutl chloride (TBCl) which allows etching of both. GaInAsP/InP and AlGaInAs/InP structures for the fabrication of buried heterostructure (BH) lasers in an MOVPE system. It is shown that the surface morphology is improved, when small ammouns of trimethyl gallium are injected during TBCl etching at reduced reactor pressure. The etching process is performed in a PH3-free atmosphere under hydrogen. Therefore, the etching temperature has to be kept at the relatively low value of 580 degreesC. GaInAsP and AlGaInAs MQW laser ridges can be formed by in situ etching under identical reactor conditions (pressure, temperature precursor flow). For Al containing lacers, however, an ex situ wet chemical etch dip is additionally required in order to avoid residue deposition which results in deteriorated surface morphology. High-quality GaInAsp and AlGaInAs ridges for BH laser applications are obtained. GaInAsP InP BH lasers fabricated by this technique exhibit excellent high-temperature characteristics. (C) 2002 Elsevier Science B.V. All rights reserved.