AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Monday Sessions
       Session NS+EM+SS-MoA

Paper NS+EM+SS-MoA3
Growth Asymmetry in InGaAsP/InAsP Superlattices Studied by Scanning Tunneling Microscopy

Monday, November 2, 1998, 2:40 pm, Room 321/322/323

Session: Cross-sectional Scanning Tunneling Microscopy of Semiconductors
Presenter: B. Grandidier, Carnegie Mellon University
Authors: B. Grandidier, Carnegie Mellon University
H. Chen, Carnegie Mellon University
R.M. Feenstra, Carnegie Mellon University
R.S. Goldman, University of Michigan
C. Silfvenius, Royal Institute of Technology, Sweden
G. Landgren, Royal Institute of Technology, Sweden
Correspondent: Click to Email
InGaAsP based multiple quantum well structures are increasingly used to fabricate optoelectronic devices. However the strain can lead to lattice relaxation processes during the growth which degrades the optical properties of these structures. To understand the differences in the photoluminescence efficiency of several superlattices composed of InGaAsP quaternary wells, we have investigated a series of InGaAsP/InGaP and InGaAsP/InAsP superlattices using cross-sectional scanning tunneling microscopy (xSTM). These superlattices were grown by metalorganic vapor phase epitaxy, with different number of periods and with or without InP interlayers inserted in the barrier. For InGaAsP/InGaP superlattices, the individual well and barrier layers are well resolved in the xSTM images. In contrast, for InGaAsP/InAsP superlattices, the InGaAsP quantum well and preceding InAsP barrier layers can be clearly seen, whereas the subsequent InAsP barriers are severely intermixed with the quantum wells. Possible mechanisms for this intermixing are described. In addition, the contrast observed in both types of superlattices has been related to the strain which exists in the layers; the compressively strained InAsP barrier protudes outwards from the (110) cleavage plane whereas the tensilely strained InGaP barrier contracts inwards. Finite element computations are used to quantify these elastic relaxation effects of the cleavage surface.