Characterisation and Control of Defects in Semiconductors Understanding the formation and introduction mechanisms of defects in semiconductors is essential to understanding their properties. Although many defect-related problems have been identified and solved over the past 60 years of semiconductor research, the quest for faster, cheaper, lower power, and new kinds of electronics generates an ongoing need for new materials and properties, and so creates new defect-related challenges. This book provides an up-to-date review of the experimental and theoretical methods used for studying defects in semiconductors, focussing on the most recent developments in the methods. These developments largely stem from the requirements of new materials - such as nitrides, the plethora of oxide semiconductors, and 2-D semiconductors - whose physical characteristics and manufacturing challenges are much more complex than in conventional Si/Ge or GaAs. Each chapter addresses both the identification and quantification of the defects and their characteristics, and goes on to suggest routes for controlling the defects and hence the semiconductor properties. The book provides valuable information and solutions for scientists and engineers working with semiconductors and their applications in electronics.
Inspec keywords: crystal defects; semiconductor doping; positron annihilation; ion beam effects; microscopy; silicon; luminescence; semiconductor materials; ion implantation; magnetic resonance
Other keywords: semiconductor defects; microscopy; ion implantation; point defect luminescence; ion beam analysis; muons; magnetic resonance methods; elemental semiconductors; first principles methods; channelling; electrically active defects; positron annihilation spectroscopy; 3D atomic-scale studies; ion beam modification; silicon; vibrational spectroscopy; ion beam effects; semiconductor doping
Subjects: Radiation effects (semiconductor technology); Semiconductor doping; Other luminescence spectra and radiative recombination (condensed matter); Doping and implantation of impurities; Semiconductor theory, materials and properties; Monographs, and collections; Photoluminescence (condensed matter); Ion beam effects; Defects in crystals; Positron annihilation (condensed matter); General electrical engineering topics
In this chapter, characterization of electrically active defects is discussed and transient capacitance measurement techniques are addressed. The chapter starts by introducing the main properties describing the electrical activity of a defect, before techniques to measure these properties using thermal and optical emission are discussed. Key techniques based on measuring capacitance transients are reviewed, with particular emphasis on DLTS, including how DLTS can be utilized for direct measurements of capture cross sections and defect profiles. The latter part of the chapter shows examples of use, where defect studies in silicon is chosen as a well established material where most of the defect levels are identified, but where fundamental knowledge of the defects can still be gained. Defects in zinc oxide (ZnO) is also discussed and chosen as a less studied material where direct identification of the origin of the defect levels remains an important challenge.
In this chapter, phenomenological theories of PL are presented and compared with experimental results on PL from wide-bandgap semiconductors, primarily GaN. Types of electron transitions leading to PL are defined in Section 2.2. The rate equations model and the configuration-coordinate (CC) model are presented in Section 2.3. In particular, we will show how to estimate the concentrations of defects and reveal their important characteristics such as the energy levels, carrier capture coefficients, electron-phonon coupling strength, excited states.
This chapter provides an overview of the theory, experimental methods, and examples of vibrational spectroscopy applied to defects in semiconductors. Additional information about IR spectroscopy and Raman scattering is discussed. Local vibrational modes in semiconductors are reviewed. There are also reviews for specific materials systems such as defects in silicon, III-V semiconductors and ZnO, and hydrogen in compound semiconductors.
In this chapter, we will focus on the study by EPR of point defects in semiconductor materials. Indeed, impurities, vacancies, anti -sites and complexes of them, in a diamagnetic material, may exhibit a local electronic reconstruction favoring unpaired electrons, and consequently, such defects have a nonzero electon spin. Of course, point defects may exist in an S = 0 state and then be EPR silent. Nevertheless, in semiconductors, most of the point defects have several charge states in the gap, and generally, each of them corresponds to a different spin state. Changing the defect charge state by electrical polarization or by light irradiation is then an efficient mean to reveal and detect the defects by EPR.
The aim of this chapter is to provide an introduction and overview of using muons to study defects in semiconductors for an audience with a background in material science. First is a general tutorial to relevant models and discussion of the muon-based techniques that have been important to the semiconductor field. The latter portion of this chapter highlights results from selected studies on semiconductors to demonstrate and describe some contributions that muon spin research (SR) techniques have made to the semiconductor community in recent years.
In summary, PAS gives microscopic information about vacancy defects in semiconductors in the concentration range 10 15 -10 19 cm -3 . The positron lifetime is the fingerprint of the open volume associated with a defect, and it can be used to identify mono- and divacancies and larger vacancy clusters. Doppler broadening of the annihilation radiation, on the other hand, can be used to identify the nature of the atoms surrounding the vacancy. Consequently, vacancies on different sub lattices of a compound semiconductor can be distinguished, and impurities associated with the vacancies can be identified. The charge state of a vacancy defect can be determined by the temperature dependence of the positron -trapping coefficient, and positron localization into Rydberg states around negative centers yields information about ionic acceptors that have no open volume. Importantly, as shown in this chapter, the methods based on positron annihilation are not restricted by the nature or physical dimensions of the semiconductor. Defects can be studied in narrow- and wide-bandgap semiconductor materials in samples of any conductivity. Bulk crystals as well as thin films can be subjected to the experiments and defects identified.
This chapter describes typical approaches and levels of approximation and the common sources of uncertainties encountered. On one hand, it provides a generalized framework for carrying out defect calculations. On the other hand, it is intended as a guide to experimentalists how to read theory papers, assess conclusions, and interact with theorists.
In this chapter, the authors discuss microscopy techniques that can be useful in addressing defects in semiconductors. They focus on three main families: scanning probe microscopy, scanning electron microscopy and transmission electron microscopy. They first address the basic principles of the selected microscopy techniques In discussions of image formation, they elucidate the mechanisms by which defects are typically imaged in each technique. Then, in the latter part of the chapter, they describe some key examples of the application of microscopy to semiconductor materials, addressing both point and extended defects and both two-dimensional (2D) and three-dimensional (3D) materials.
In this chapter, the role of APT in the investigation of extended defects and solute segregation in semiconductors is discussed on the basis of several salient studies mainly carried out in our laboratory (Groupe de Physique des Materiaux) and dealing with one-dimensional (1D) (dislocations), two-dimensional (2D) (interfaces, SFs, GBs) and 3D defects (clusters, QDs). The principles of APT are first presented including a discussion of limitations in terms of spatial resolution and quantitativity. Results and performances are also compared to those of SIMS.
In this chapter, we give an overview of the basic physics and experimental method behind the conventional ion-beam modification of semiconductors. In particular, we describe the basic understanding of the keV ion implantation process used for doping Si and the fascinating amount of materials physics involved in the path from the initial implantation to the dopant activation. We also describe two recent developments related to the physics of implantation: the mechanisms of surface ripple formation and time-resolved experiments used to shed new light on defect migration and interaction processes.
This chapter deals with the use of ion beam analysis (IBA) techniques, in particular in channeling geometry, to study defects in semiconductors. After a tutorial (Section 11.1) introducing the basic principles of IBA and channeling techniques, selected examples of their use to characterize defects (e.g., lattice location of dopants and implantation damage) are described in Section 11.2. Finally, Section 11.3 consists of a brief outlook into future developments and applications.
