We present a comprehensive review of implementation and application of Laplace deep-leve1 transient spectroscopy (LDLTS). The various approaches that have been used previously for high-resolution DLTS are outlined and a detailed description is given of the preferred LDLTS method using Tikhonov regularization. The fundamental limitations are considered in relation to signal-to-noise ratios associated with the measurement and compared with what can be achieved in practice. The experimental requirements are discussed and state of the art performance quantified. The review then considers what has been achieved in terms of measurement and understanding of deep states in semiconductors through the use of LDLTS. Examples are given of the characterization of deep levels with very similar energies and emission rates and the extent to which LDLTS can be used to separate their properties. Within this context the factors causing inhomogeneous broadening of the carrier emission rate are considered. The higher resolution achievable with LDLTS enables the technique to be used in conjunction with uniaxial stress to lift the orientational degeneracy of deep states and so reveal the symmetry and in some cases the structural identification of defects. These issues are discussed at length and a range of defect states are considered as examples of what can be achieved in terms of the study of stress alignment and splitting. Finally the application of LDLTS to alloy systems is considered and ways shown in which the local environment of defects can be quantified.

By tailoring the boundary of a narrow semiconductor channel to break its symmetry, we have realized a type of nanometer-scale nonlinear device, which we refer to as self-switching device (SSD). An applied voltage V not only changes the potential profile along the channel direction, but also either widens or narrows the effective channel depending on the sign of V. This results in a diode-like characteristic but without the use of any doping junction or barrier structure. The turn-on voltage can also be widely tuned from virtually zero to more than 10 V, by simply adjusting the channel width. The planar and two-terminal structure of the SSD also allows SSD-based circuits to be realized by only one step of lithography.

The term junction spectroscopy embraces a wide range of techniques used to explore the properties of semiconductor materials and semiconductor devices. In this tutorial review we describe the most widely used junction spectroscopy approaches for characterizing deep-level defects in semiconductors and present some of the early work on which the principles of today's methodology are based. We outline ab-initio calculations of defect properties and give examples of how density functional theory in conjunction with formation energy and marker methods can be used to guide the interpretation of experimental results. We review recombination, generation and trapping of charge carriers associated with defects. We consider thermally driven emission and capture and describe the techniques of Deep Level Transient Spectroscopy (DLTS), high resolution Laplace DLTS, admittance spectroscopy and scanning DLTS. For the study of minority carrier related processes and wide gap materials we consider Minority Carrier Transient Spectroscopy (MCTS), Optical DLTS (ODLTS and DLOS) together with some of their many variants. Capacitance, current and conductance measurements enable carrier exchange processes associated with the defects to be detected. We explain how these methods are used in order to understand the behaviour of point defects, the determination of charge states and negative-U (Hubbard correlation energy) behaviour. We provide, or reference, examples from a wide range of materials including Si, SiGe, GaAs, GaP, GaN, InGaN, InAlN and ZnO.

Silicon solar cells containing boron and oxygen are one of the most rapidly growing forms of electricity generation. However, they suffer from significant degradation during the initial stages of use. This problem has been studied for 40 years resulting in over 250 research publications. Despite this, there is no consensus regarding the microscopic nature of the defect reactions responsible. In this paper, we present compelling evidence of the mechanism of degradation. We observe, using deep level transient spectroscopy and photoluminescence, under the action of light or injected carriers, the conversion of a deep boron-di-oxygen-related donor state into a shallow acceptor which correlates with the change in the lifetime of minority carriers in the silicon. Using ab initio modeling, we propose structures of the BsO2 defect which match the experimental findings. We put forward the hypothesis that the dominant recombination process associated with the degradation is trap-assisted Auger recombination. This assignment is supported by the observation of above bandgap luminescence due to hot carriers resulting from the Auger process.

A quantitative improvement in deep-level transient spectroscopy (DLTS) resolution has been demonstrated by using Laplace transform method for the emission rate analysis. Numerous tests performed on the software used for the calculations as well as on the experimental setup clearly demonstrated that in this way the resolution of the method can be increased by more than an order of magnitude. Considerable confidence in this approach was gained through measurements of a selection of well-characterized point defects in various semiconductors. The results for platinum in silicon and EL2 in GaAs are presented. For each of these cases conventional DLTS give broad featureless lines, while Laplace DLTS reveals a fine structure in the emission process producing the spectra.