Surface‐emitting lasers of low‐threshold 1.3‐μm GaInAsP/InP circular planar‐buried heterostructure

Abstract

AbstractThe GaInAsP/InP circular planar‐buried heterostructure is a promising structure to realize a low‐threshold 1.3‐μm surface‐emitting laser for continuous operation at room temperature. In the conventional regrowth process, pinholes which depend on the crystalline orientation of the circular active region tend to occur, resulting in the increase of nonradiative current. As a result, it has been difficult to achieve room temperature oscillation.To solve this problem, the planar‐buried structure which could be formed by one liquid‐phase epitaxial step without using a mask was adopted to fabricate mesa‐type surface‐emitting lasers. As a result, the reproducibility in forming the buried structure was improved and the non‐radiative current decreased. the resultant devices showed stable electrical and optical characteristics.When the laser cavity was formed by using SiO2/Si dielectric multilayer mirrors, continuous oscillation was observed at 77 K and the threshold currents of 15 devices were lower than 15 mA. the lowest threshold current was 2.2 mA.In the room‐temperature pulse operation, the threshold current was 34 mA, the lowest among the values ever reported. Pulse oscillation was observed at 45°C and continuous operation was observed even at −57°C.If reflecting mirrors with a high thermal conductivity are introduced, the temperature for continuous operation will increase and it will be possible to realize continuous operation at room temperature.