Studies of internal structure in InGaAsP/InP-based lasers using atomic force microscopy in combination with selective etching

We have used cross-sectional atomic force microscopy in combination with do pant-selective etching to study structural details in InGaAsP/InP-based las er diodes. The different etch rates of p-type, n-type, and semi-insulating InP allowed us to relate topographic features in atomic force images of etc hed lasers to changes in the electrical characteristics of the semiconducti ng material. This allowed us to follow, e.g., the interdiffusion of Fe and Zn across the interface between p-InP:Zn and semi-insulating InP:Fe. A nonl inearity in the light-output power response suggests that this interdiffusi on has given rise to leakage currents in the structure. In addition, electr on-beam induced-current images imply a widening of the depletion layer at t his interface. Effects due to Zn diffusion across the interface between p-I nP:Zn and n-lnP:Si could also be observed. Unexpected traces of an unavoida ble contamination at surfaces exposed to the atmosphere before regrowth was found in both atomic force microscopy images and cross-sectional transmiss ion electron microscopy images of the same laser type. The results illustra te how the atomic force microscopy in combination with selective etching ca n serve as a simple and convenient tool for detailed structural studies of InGaAsP/InP-based lasers. (C) 1999 The Electrochemical Society. S0013-4651( 98)03-106-1. All rights reserved.