Optical in situ monitoring, exploiting the interference of monochromat
ic radiation reflected from the surface being chemically etched and fr
om the deeper interfaces of semiconductor layers, was utilized to moni
tor the etch process of layered AlGaAs/AlAs/GaAs structures, The descr
ibed method is applicable in controlled etching of heterostructures in
order to terminate the etch process precisely and it is also suitable
for analysis and diagnostics of epitaxially grown layers and for cali
bration of etch rates. (C) 1998 John Wiley & Sons Ltd.