CATASTROPHIC DEGRADATION LINES AT THE FACET OF INGAASP/INP LASERS INVESTIGATED BY TRANSMISSION ELECTRON-MICROSCOPY

Material transformations occurring at the facets of optically ''stressed'' planar InGaAsP/InP diode lasers have been investigated by transmission electron microscopy and energy dispersive x-ray spectroscopy. Catastrophic degradation lines (CDLs) which are characteristic of catastrophic optical damage are observed for optical power densities similar to 10(7) W/cm(2). Analysis of the microstructure reveals a series of 150 nm wide GaAs-rich tracks and the formation of unique void/InGa-rich precipitate pairs within the InCaAsP active layer. These observations suggest that the formation of local group LII-rich regions is the first stage in the formation of CDLs. Subsequently, the strong absorption of the impinging laser beam leads to propagation of an InGa-rich melt, thereby producing the GaAs-rich tracks through a process similar to liquid phase epitaxy. These results are discussed in the context of standard physical models for CDLs. (C) 1995 American Institute of Physics.