THE INFLUENCE OF ALUMINUM CONCENTRATION ON PHOTOELECTROCHEMICAL ETCHING OF FIRST-ORDER GRATINGS IN GAAS ALGAAS/

We present a set of experiments which systematically clarifies the enh ancement of photoelectrochemical (PEC) etching due to the mole fractio n of aluminum in AlxGa1-xAs. The spatial resolution of gratings etched in Al0.3Ga0.7As is as much as three times greater than the spatial re solution of gratings etched in GaAs, so that the smallest practical gr ating period is about 0.3 mu m, as compared with about 0.7 mu m using previous techniques. This technique enabled PEC fabrication of first o rder gratings for waveguide outcouplers. The lower hole mobility of Al xGa1-xAs is proposed as a possible explanation for this grating resolu tion improvement. (C) 1995 American Institute of Physics.