The threshold current of InGaAsP etched mesa buried heterostructure (EMBH) lasers is strongly influenced by the position of the active layer in the etched mesa. Transmission electron microscopy results are presented which show the presence of a thin planar disorder along the etched 111A interface. Nonradiative recombination of carriers is believed to be responsible for the increased threshold current of EMBH lasers whose active region is bounded by 111A interface. Lasers with threshold current as low as 14 mA at 30 °C have been fabricated by proper placement of the active layer and by optimizing layer thicknesses and doping levels.