Die-bonding study for double-channel ridge waveguide AlGaInP laser diodes

Abstract

A1GaInP visible laser diode is one of the most attractive light sources because it is of great importance in many applications such as optical information storage systems, laser printers, bar code readers and laser pointers. A1GaInP laser diode has a broad emission spectrum of 610 to 690 nm that makes it a versatile and outstanding light source. In addition, AlGaInP laser diodes with low threshold currents have also been realized. The laser diode used for our study is a 660-nm compressively strained A1GaInP with a structure of double-channel ridge waveguide (DCRW). Laser diodes with DCRW structure are widely used for commercialized low-cost and low-power laser diode applications owing to their relatively low threshold currents, easy fabrication and high yield as compared to laser diodes with selectively buried ridge waveguide structure. However, the top surfaces of DCRW laser diodes are non-flat and heat dissipation becomes a main problem for DCRW A1GaInP laser diodes. Especially, if comparing A1GaInP laser diodes with A1GaAs laser diodes, A1GaInP laser diodes have lower thermal conductivity and higher thermal resistance. Therefore, a good die bonding becomes important for improving the heat dissipation of DCRW AlGaInP laser diode chips. Most studies for die bonding have been focused on the choice of submounts or heat sinks with large heat conductivity. Few investigators study how to improve the quality of die bonding and avoid leading voids inside bonded interface. In this study, different p-metal materials, p-metal annealing environments, die-bonding steps and die-bonding equipment were adopted to change die-bonding conditions. Their influences on thermal dissipation capability were also investigated.