USE OF ATOMIC-FORCE MICROSCOPY FOR ANALYSIS OF HIGH-PERFORMANCE INGAASP INP SEMICONDUCTOR-LASERS WITH DRY-ETCHED FACETS/

We report on the use of an atomic force microscope (AFM) to directly m easure the quality of InGaAsP/InP laser facets formed by a CH4:H-2:Ar reactive ion etching process. From the AFM data, we obtain values for rms surface roughness and transverse angular tilt that have previously only been estimated through laser operating characteristics or inferr ed from scanning electron microscope analysis. The etched facet reflec tivity, calculated from device slope efficiency data and far-field bea m profiles, is in excellent agreement with AFM measurements. We show m ethane-based dry etching can achieve a rms facet roughness of 22 nm. T his value surpasses the generally accepted roughness parameter of lamb da/10 and is competitive with the best chlorine-based facet etching to date. We also report a transverse angular facet tilt of 2 degrees, wh ich we believe to be the most vertical, CH4-based facet etch reported to date. The output performance of these devices is nearly identical t o cleaved devices. (C) 1998 American Vacuum Society.