Ion Beams for synthesis and modification of nanostructures in semiconductors
- PDF / 425,817 Bytes
- 12 Pages / 432 x 648 pts Page_size
- 63 Downloads / 213 Views
Ion Beams for synthesis and modification of nanostructures in semiconductors Anand P. Pathak*, N. Srinivasa Rao, G. Devaraju, V. Saikiran and S. V. S. Nageswara Rao School of Physics, University of Hyderabad, Hyderabad 500046, A P, India ABSTRACT Swift heavy ion irradiation is one of the most versatile techniques to alter and monitor the properties of materials in general and at nanoscale in particular. The materials modification can be controlled by a suitable choice of ion beam parameters such as ion species, fluence and incident energy. It is also possible to choose these ion beam parameters in such a way that ion beam irradiation can cause annealing of defects or creation of defects at a particular depth. Here, we present a review of our work on swift heavy ion induced modifications of III-V semiconductor heterostructures and multi-quantum wells in addition to synthesis of Ge nanocrystals using atom beam co-sputtering, RF magnetron sputtering followed by RTA, swift heavy ion irradiation, respectively. We also present the growth of GeO2 nanocrystals by microwave annealing. These samples were studied by using XRD, Raman, PL, RBS and TEM. The observed results and their explanation using possible mechanisms are discussed in detail.
----------------*Corresponding author. Tel.: +91 40 23010181/23134316; fax: +91 40 23010181/23010227. E-mail address: [email protected] (A.P. Pathak).
INTRODUCTION In III-V compounds, introduction of another column III or column V element leads to small change in lattice parameter accompanied by corresponding variation in energy band gap of original semiconductor [1]. For example introduction of small amounts of Indium or Aluminum in GaAs or GaN would result in a change of lattice parameter and band gap. If such layers are deposited on the parent substrate, the small lattice mismatch induces tensile or compressive strain in the deposited epilayer. This strain increases with thickness of the deposited layer or with concentration of the doped elements. Beyond a certain critical value, the strain relaxes into misfit defects. Such misfit dislocations and interfaces play a crucial role in the performance of strained heterostructure devices. Several researchers have investigated the nature of these dislocations and the mechanism of their formation [1–2]. Dislocation formation due to strain relaxation beyond a critical layer thickness is a limitation in strained heterostructures. To overcome this limitation several buffer structures have been proposed [3–4], which proved to be the most efficient solution. The optoelectronic device performance deteriorates drastically due to generation of these misfit defects [5-6]. This leads to possibility of fabricating Strained Layer Superlattice (SLS) with equal thickness of alternate layers of small lattice mismatch with thickness below critical value for strain relaxation. The usefulness of these structures is that, they offer precise control over the states and motions of charge carriers in semiconductors [1]. As a result, the electronic and optoelec
Data Loading...
