Scanning capacitance microscopy investigations of buried heterostructure laser structures

In this work, InP-based buried heterostucture lasers are used to demonstrate the utility of scanning capacitance microscopy (SCM) for characterising complex device structures. The lasers use p-n junctions formed by selective regrowth of p and n doped InP layers around a mesa for current confinement. For comparison, the regrowth was performed by liquid phase epitaxy (LPE) and metal organic vapour phase epitaxy (MOVPE). Our investigations show that scanning capacitance microscopy is capable of detecting the p-n junctions formed at different regions of the device and thereby allows visualisation of the current confinement regions. Variations in the imaged depletion regions are attributed to doping variations due to modification of the regrowth process by the mesa. The SCM data show significant differences between the devices regrown by LPE and MOVPE and the results are consistent with the different regrowth mechanisms. Finally, the implications of the SCM data on device performance are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.