Low-threshold current AlGaAs/GaAs-distributed feedback laser grown by two-step molecular beam epitaxy

AlGaAs/GaAs-distributed feedback (DFB) lasers with oxide-stripe structure were fabricated by a two-step molecular beam epitaxial (MBE) growth for the first time. The large coupling coefficient of 90 cm
^-1
and the threshold current as low as 165 mA at room temperature were obtained with the second-order gratings. The characteristic temperature T
0
was as high as 210 K. Single longitudinal-mode oscillation was observed up to
I/I_{th} = 1.5
and from 0 to 50°C without any mode hopping. The wavelength variation from device to device was ±5 Å. The dependence of the coupling coefficient on the device structure was calculated, and it was shown that MBE is much more advantageous than LPE to enhance the coupling coefficient.