High-performance 1.3-μm InAs/GaAs quantum-dot lasers with low threshold current and negative characteristic temperature

A high-growth-temperature step used for the GaAs spacer layer is shown to significantly improve the performance of 1.3-mu m multilayer InAs/GaAs quantum-dot (QD) lasers. The high-growth-temperature spacer layer inhibits threading dislocation formation, resulting in enhanced electrical and optical characteristics and hence improved laser performance. The combination of high-growth-temperature GaAs spacer layers and high-reflectivity (HR) coated facets has been utilized to further reduce the threshold current and threshold current density (J(th)) for 1.3-mu m InAs/GaAs QD lasers. Very low continuous-wave room-temperature threshold current of 1.5 mA and a threshold current density of 18.8 A/cm(2) are achieved for a 3-layer device with a 1 min long HR/HR cavity. For a 2-mm cavity the continuous-wave threshold current density is as low as 17 A/cm(2) at room temperature for an HR/HR device. An output power as high as 100 mW is obtained for a device with HR/cleaved facets. The high-growth-temperature spacer layers have only a relatively small effect on the temperature stability of the threshold current above room temperature. To further increase the characteristic temperature (To) of the QD lasers, 1.3-mu m InAs/GaAs QD lasers incorporating p-type modulation doping have been grown and studied. A negative To and J(th) of 48 A/cm(-2) at room temperature have been obtained by combining the high-growth-temperature GaAs spacer layers with the p-type modulation doping of the QDs.