The transport properties and defect recombination activity of 1.3 mu m and 1.55 mu m laser heterostructures grown on different step-and linearly-graded InGaAs buffer layers are evaluated by means of electron-beam-induced-current. These transport parameters are related to the threading dislocation density and interface roughness obtained by means of transmission electron microscopy (TEM). The defect strength gamma of dislocations, estimated from EBIC measurements, gives gamma approximate to 10(3) - 10(4) mu m(-2). The EPIC data allow us to conclude that the interface roughness plays a fundamental role in laser degradation. The step-graded buffers investigated in this contribution exhibit an enhanced planarity and, hence, the lasers grown on them show better transport properties.