This paper is based on a comprehensive review of the literature and our own studies. We present a summary of the theoretical models and related empirical expressions to evaluate parameters related to the carrier transport within Si/SiGe heterostructures. The models and expressions include the effects of alloy composition and mechanical strain on the band structure of Si/SiGe alloys and the corresponding interfaces. They are presented in a form suitable for implementation in various types of device simulators. Important parameters, such as the band structure of strained or relaxed SiGe, the conduction and valence band offsets in the Si 1−x Ge x /Si 1−y Ge y heterostructures, the effective transport masses and the densities of states, have been calculated and shown to be in good agreement with existing experimental and theoretical results. Analytical expressions of those parameters as a function of Ge composition of the SiGe alloy have been given for strained Si on relaxed Si 1−y Ge y substrate and strained Si 1−x Ge x on Si substrate.
Bandgap engineering of photocatalysts is a common approach to achieving high effective utilization of solar resource. However, the difficulty in achieving bandgap narrowing and high activity simultaneously seems to be irreconcilable via the traditional modification pathway. Herein, we have substituted iodine for a fraction of bromine atoms in BiOBr to overcome this restriction and provided some deep-seated insights into how the substitution boosts the photocatalytic properties. The substituted BiOBr 0.75 I 0.25 exhibited exceptional photoactivity, with photon-to-current conversion efficiency approximately 6 times greater than TiO 2 in UV region, and more than 10 times higher than BiOBr or BiOI in visible-light region. We found that the substitution narrowed the bandgap, facilitated the diffusion of electron with small effective mass, as well as induced oxygen vacancies on [Bi 2 O 2 ] 2+ layers. By virtue of the stronger dipole moments produced, the enhancement of intrinsic electric fields between [Bi 2 O 2 ] 2+ and halogen slabs was achieved in BiOBr 0.75 I 0.25 ; thereby the distance the photogenerated electron could diffuse was sufficient to inhibit the recombination. Our findings not only shed light on the potential properties of hybrid-halide photocatalysts but also provide a strategy for developing high efficiency catalysts.
Patent and regulatory exclusivity shall constitute incentives for pharmaceutical companies to develop new drugs. This study aims to investigate the differences in the patent term extension (PTE) and regulatory exclusivity between China and the United States, and to evaluate their potential impact on the market exclusivity period of novel drugs. Small‐molecule novel drugs with their first indication approved in China and the United States between 2018 and 2021 were evaluated regarding their PTE and regulatory exclusivity. The PTE length of the China‐approved drugs was calculated by simulation, whereas that of the US‐approved drugs was extracted from the United States Patent and Trademark Office. Thirty‐two and 107 novel drugs approved in China and the United States, respectively, were included in the study. The PTE length of the US‐approved drugs calculated by the China‐PTE method was significantly longer than that calculated by the US‐PTE method. Patent extensions should be granted for 91% of new drugs in China and 82% in the United States. The simulated median PTE length of novel drugs approved in China was significantly higher than that of the United States (5.0 vs. 2.9 years, P < 0.05). It can be expected that the implementation of the PTE policy in China would significantly extend the period of market exclusivity for novel drugs similar to that of the United States. China should fully evaluate the potential impact of the PTE policy on the market exclusivity of novel drugs and provide better incentives to the development of novel drugs in addressing unmet clinical needs when developing its regulatory exclusivity policy.
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