Transmission cathodoluminescence as a screening technique for rake lines in /Al, Ga/As DH laser material

The use of transmission cathodoluminescence (TCL) as a nondestructive screening technique for rake lines in (Al, Ga)As double heterostructure laser material is examined. For TCL evaluation the double heterostructure laser slice is mounted epitaxial side up on a PN silicon photodiode, and the electron beam of the scanning electron microscope is scanned over the top of the slice. In order to form a high quality TCL image of rake lines in the thin active layer, the electron beam must penetrate to the active layer but fall short of the substrate. After TCL evaluation a portion of the slice is processed into broad area devices (250 x 380 sq microns) for room temperature pulse testing of the light-output/current characteristic. Results show significant increases in threshold current density being observed with increasing severity of rake lines. TCL evaluation is shown to correlate well with the fraction of good devices for both broad area and stripe geometry laser configurations.