LOW-THRESHOLD GAINASSB/GAALASSB DOUBLE-HETEROSTRUCTURE LASERS GROWN BY LPE

We report the lowest threshold current density Ga0.86In0.14As0.19Sb0.87/Ga0.79Al0.27As0.02Sb0.98 2.2 mum lasers grown by LPE. Using transverse far-field patterns and theoretical calculations for the fundamental mode, we estimated the value of the active layer refractive index as 3.78. We also show that the development of low-threshold current stripe lasers is limited by an excessive current spread in the low-resistivity p-type active layer. This is partly solved by making the active region n-type. The minimum I(th) obtained for n-type active layers was 290 mA compared to 800 mA for p-type active layers, the broad-area threshold current being the same (3 kA/cm2) in both cases.