Results of InP/GaInAsP interface study using the contact probe profiling method are presented. Results of the interface study are given for λ=1.3 μm laser heterostructures. A correlation is shown between the shape of the interface in the heterostructure and the threshold current of lasers produced from such heterostructures. The correlation of the results with secondary ion mass spectroscopy measurements is also demonstrated. An idea is given of how to detect the very close spaced interfaces with the contact probe method. Its realization with the use of Kr+ion bombardment is shown. In conclusion the ballistic electron emission microscopy is suggested as an attractive new method for characterization of shallow heterostructures.