Polyimide-isolated ridge waveguide InGaN/GaN laser diodes based on back-ward exposure

The manufacture of metal electrode window on the ridge structure of laser diodes (LDs) is a confused issue in the LDs fabrication process. We show that the processing of the self-aligned step and negative photosensitive polyimide (NPP) thermal imidization which can achieve both accurate alignment of p-electrode window on the ridge structure and integrated dielectric layer at once time. This back word exposure technic can effectively simplify the process of accuracy of alignment and avoid etching of isolating layer. The optical and electrical performance of the LD chip measured at room temperature under a pulse current condition (the current duty ratio was 25%) were shown. The output optical power was greater than 20 mW, at 7.7 V operating voltage, and the reversed current is 3.9 × 10−5 mA when the bias voltage is −5 V. A lasing peak wavelength at around 442 nm became dominant at 320 mA. Our results provide an alternative effective approach to fabricate the well behavior LDs.