Abstract
Growth and device characteristics of an index-guided GaAs/AlGaAs multiquantum-well (MQW) laser, called a pair-groove-substrate (PGS) MQW laser, are described in detail. The laser structure is fabricated by using single-step molecular-beam epitaxy on a (001) GaAs substrate with a pair of etched grooves along the 〈11̄0〉 direction. A mesa between a pair of grooves, where the lasing action occurs, becomes narrow during growth, and the narrow mesa offers lateral waveguiding that stabilizes a fundamental transverse mode. The superior crystalline quality of the mesa top, which is examined by a microprobe photoluminescence technique, serves to lower the lasing threshold currents. The lasers with mesa widths below 2 μm show stable transverse mode operation with a low threshold current of 20 mA, as well as a high external differential quantum efficiency of 68%. The low threshold and high characteristic temperature accomplish a high-temperature continuous-wave operation at 153 °C for the lasers mounted on silicon heat sinks.
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