Investigations have been done by Scanning Capacitance Microscopy (SCM) on GaAs/AlGaAs buried-heterostructure lasers in order to demonstrate the capability of SCM for high resolution electrical characterisation of complex device structures. The SCM is shown to provide a complete 2D map of the device structure, including doping variations, location of p-n junctions and regrown interfaces. By varying the ac-bias, various regrown interfaces were characterised. The interface between the n-type regions and the regrown layer show a characteristic contrast peak due to band-bending. A zero SCM signal (dC/dV) is observed for the regrown layer both close to and far away from the mesa, and confirms very low free carrier density in the layers. Furthermore, the uniformly zero signal in the regrown layer suggests uniform Fe incorporation.