Size and critical thickness evolution during growth of stacked layers of InAs/InP(001) quantum wires studied by in situ
- PDF / 568,442 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 108 Downloads / 211 Views
T5.3.1
Size and critical thickness evolution during growth of stacked layers of InAs/InP(001) quantum wires studied by in situ stress measurements David Fuster, María Ujué González, Luisa González, Yolanda González, Teresa Ben1, Arturo Ponce1 and Sergio I. Molina1 Instituto de Microelectrónica de Madrid (CNM-CSIC), Tres Cantos, Madrid, Spain. 1 Departamento de Ciencia de los Materiales e I. M. y Q. I., Universidad de Cádiz, Puerto Real, Cádiz, Spain. ABSTRACT Size and spatial distribution homogeneity of nanostructures is greatly improved by making stacks of nanostructures separated by thin spacers. In this work we present in situ and in real time stress measurements and reflection high energy electron diffraction (RHEED) observations and ex situ transmission electron microscopy (TEM) characterization of stacked layers of InAs quantum wires (QWr) separated by InP spacer layers, d(InP), of thickness between 3 and 20 nm. For d(InP) < 20 nm, the amount of InAs involved in the newly created QWr from the 2nd stack layer on, exceeds that provided by the In cell. Our results suggest that in those cases InAs 3D islands formation starts at the P/As switching and lasts during further InAs deposition. We propose an explanation for this process that is strongly supported on TEM observations. The results obtained in this work imply that concepts like the existence of a critical thickness for 2D3D growth mode transition should be revised in correlated QWr stacks of layers. INTRODUCTION It is now well established that the size homogeneity and spatial distribution of self-assembled nanostructures can be greatly improved by stacking several layers [1-4]. In this context, the vertical stacks of self-assembled InAs quantum wires (QWr) grown on InP(001) are of particular technological interest, as these nanostructures emit light at 1.30 and 1.55 µm [5-7], and so could be used in the active region of advanced lasers for telecommunications. In nanostructures stacks, the partially relaxed buried nanostructures produce inhomogeneous strain fields that propagate towards the surface where the next nanostructure layer is formed. Consequently there is a vertical correlation between nanostructures. The spacer layer thickness emerges then as a decisive parameter, which for a given material system depends on the specific size of the buried nanostructures. In this work, we have studied the growth of multilayers of InAs/InP(001) QWr with different spacer layer thickness, d(InP), by in situ and in real time stress measurements and reflection high energy electron diffraction (RHEED). A strong influence of the spacer layer thickness on QWr formation process in the 2nd and successive layers of the stack has been observed. Layers in the stack are correlated for d(InP) < 20 nm, where we have detected a reduction of the amount of deposited InAs necessary for QWr formation (detected by RHEED) together with an increase in InAs growth rate (measured by stress measurements). In order to explain the obtained results we propose a model that is strongly supporte
Data Loading...
