Abstract

High-power lasers emitting at a wavelength of 980 nm are preferred pumping sources for Er³⁺-doped fiber amplifiers and are widely used in communication systems. We have fabricated MBE-grown strained In_0.2Ga_0.8As/AlGaAs GRIN-SCH lasers with different number of quantum wells (1-3). The 8-nm-thick quantum wells are surrounded by 40-nm-thick GaAs barrier layers and Al_xGa_1-xAs graded index layers where the Al mole fraction x is linearly graded from 14 to 50 %. We have varied the thickness of the GRIN-SCH region in the range of 250 nm and 600 nm. The top contact consists of a highly doped (10²⁰cm^-3) 50-nm-thick cap layer and an evaporated TiPtAu contact metallization. The active areas with a width of 20 – 150µm have been defined by wet chemical etching. To obtain a high reliability, the structures have been passivated by a Si₃N₄ layer deposited by plasma-enhanced chemical vapor deposition (PECVD). Especially in high-power devices, the continuous optical power is limited by thermal heating. Besides a low series resistance, an effective cooling mechanism is necessary. For lowering the thermal resistance, the laser diode has been soldered junction-side down on a diamond heat spreader because of the high thermal conductivity which is about 20 times higher compared to GaAs. A 3-µm-thick eutectic AuSn layer is used as solder.

© 1996 IEEE