Nonradiative Recombination Parameters in Semiconductors : Insights from the Photothermal Deflection Technique

This book provides a comprehensive and rigorous treatment of the determination of nonradiative recombination parameters in semiconductors, with particular emphasis on the photothermal deflection technique (PTD) as a powerful, non-destructive analytical tool. By combining experimental methodologies with advanced theoretical modeling, it offers a coherent approach for understanding carrier transport and recombination mechanisms in both bulk materials and complex semiconductor structures. This book presents an up-to-date overview of photothermal techniques used in semiconductor characterization, including the Mirage Effect, photothermal radiometry, and photo-reflectance. These methods are discussed in terms of their physical principles and their capability to probe carrier transport, recombination processes, and electronic diffusivity through measurements of refractive index variations, infrared emissions, and reflectivity changes. Their relevance to modern optoelectronic device development and advanced material systems is highlighted. The experimental implementation of the photothermal deflection technique is then described in detail. This book outlines the operating principles of PTD, including thermal-wave generation under modulated optical excitation and probe beam deflection induced by refractive index gradients. The complete instrumentation is presented, covering excitation, detection, and data acquisition systems, with particular attention to signal processing and phase-sensitive detection. Subsequent chapters develop the theoretical models required for interpreting PTD measurements. A one-layer theoretical model is first introduced for bulk semiconductors, providing analytical tools for extracting key parameters such as carrier lifetime, electronic diffusivity, diffusion length, and surface recombination velocity. The discussion is then extended to a two-layer theoretical model suitable for semiconductor heterostructures, where the influence of substrates, interfaces, and surfaces must be taken into account. This approach enables accurate characterization of transport properties in layered systems and is illustrated through applications to a variety of compound semiconductors. Finally, this book presents an advanced three-layer theoretical model designed for complex heterostructures, including quantum-dot systems such as GaAs/InAs/GaAs architectures.