Surface segregation of In atoms during molecular-beam epitaxy and its influence on the energy levels in strained piezoelectric InGaAs∕GaAs and InGaN∕GaN quantum wells (QWs) are investigated theoretically. It is shown that these effects modify the electronic states in the QW and the emission energy in the photoluminescence (PL) spectra. In this work, we solve analytically the Schrödinger equation in the absence of electric field, taking into account the shape changes in the QWs due to the segregation of In atoms during the growth process of the semiconductor heterostructures. Furthermore, the influence of the built-in electric field due to the piezoelectric effect on the PL emission is calculated by considering a variational electron wave function to calculate the ground-energy transitions inside the active region in the heterostructure. In particular, we apply this model to the case of indium segregation in InGaAs∕GaAs for moderate internal electric fields. The transition energy calculations between the confined electron and hole states as a function of the well width for different temperatures and In composition are in agreement with the measured PL energy peaks.
The beetle families Carabidae and Cicindelidae, with about 40 000 species worldwide, play an increasing role in biodiversity conservation and ecological studies in Colombia, which makes a faunistic update all the more necessary. We present and analyze a checklist of the species so far described or registered from Colombia until 2020, based on published studies, and their distribution data at the department level. Carabidae are represented by 625 species and Cicindelidae by 100. Magdalena, Cundinamarca and Valle del Cauca are the departments with the highest record numbers of Carabidae, while Cicindelidae are most frequently cited from Valle del Cauca, Antioquia and Meta. The greater sampling effort in these regions is likely due to the accessibility of their natural areas from the main towns. The geographical distribution of Cicindelidae is better documented, with only 17 % of the species without mention of specific localities within the country, against 40 % in Carabidae. Hyper-diverse regions, such as the Chocó and the Amazon, are underrepresented. The number of species currently recorded is therefore estimated to be much lower than true diversity for both families.
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