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The photo-generated currents of GaAs solar cells with different lengths of space charge region are obtained and analyzed in this study. The enhanced absorption coefficient in the space charge region is adopted to calculate the photo-generated current based on the solar cell physics theory. The calculated currents coincide well with the experimental currents both under single wavelength incidence and solar spectrum irradiation conditions.

The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, GaAs based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells, photodetectors, and other photoelectric devices.

The steel-structured corridor project of the Industry Innovation Park (IIP) in Beijing adopts an overhanging design with a large size and span. In the demolition stage of the overhanging support, the steel structures will deform. In order to understand the deformation degree of the steel structures in IIP in real time and ensure construction safety, it is necessary to monitor the deformation process of the steel structures. We select the points sensitive to deformation and key parts of the steel structures as monitoring points, and make an automatic deformation monitoring scheme. We use the deformation monitoring system based on measuring robots and Global Navigation Satellite Systems (GNSS) to monitor the steel structures. Then we compare and analyze the deflection values measured by the two monitoring systems. The results from the two monitoring systems are relatively consistent and mutually verify. The results also show that the steel structures are obviously deformed due to the influence of unloading construction. In addition, deflection values obtained by deformation monitoring are compared with the deformation limit of the key steel components derived from the design code. The results show that the deflection values are within a reasonable range, indicating that the construction design of the steel structures in IIP is reasonable and the steel structures are in safe conditions. The deformation monitoring systems based on measuring robots and GNSS technology used in this paper meet the monitoring requirements in the construction phase and can play their value in similar projects.

The influence of excessive H2 flow during barrier growth on optical and electrical properties of InGaN light-emitting diodes (LEDs) are investigated in this study. The room temperature photoluminescence of LEDs decays with excessive H2 treatment. Temperature-dependent photoluminescence (TDPL) reveals an increase of the density and a decrease of the activation energy of deep non-radiative recombination centers in the H2 treated LEDs. The external quantum efficiency (EQE) of the LEDs suffers from excessive H2 treatment. The leakage current on the reverse and forward sides of the LEDs are reduced significantly when treated with H2, which may be due to the suppressed Poole–Frenkel effect.

With economic development, people often ignore the changes to the ecological system of the constructed area. However, whenever we change an ecosystem, it is possible to limit or remove ecosystem services. Therefore, we measure the degradation of ecosystem service values before and after a development project by establishing ecological health evaluation and social-ecological economic compound model. Through the establishment and calculation of these models, we find that in order to achieve scientific and sustainable development in a certain region, the restoration value of the ecosystem must be taken into consideration, and the optimal solution of social, ecological and economic composition can be found based on the actual geographical situation. The method in this paper is more concise and intuitive, which has a strong economic measurement effect on the policy of minimum ecological damage in current engineering construction, and the optimal solution can be find according to engineering requirements to ensure the balance between environment and construction.

The resonant excitation is used to generate photo-excited carriers in quantum wells to observe the process of the carriers transportation by comparing the photoluminescence results between quantum wells with and without a p—n junction. It is observed directly in experiment that most of the photo-excited carriers in quantum wells with a p—n junction escape from quantum wells and form photocurrent rather than relax to the ground state of the quantum wells. The photo absorption coefficient of multiple quantum wells is also enhanced by a p—n junction. The results pave a novel way for solar cells and photodetectors making use of low-dimensional structure.

According to the well-established light-to-electricity conversion theory, resonant excited carriers in the quantum dots will relax to the ground states and cannot escape from the quantum dots to form photocurrent, which have been observed in quantum dots without a p–n junction at an external bias. Here, we experimentally observed more than 88% of the resonantly excited photo carriers escaping from InAs quantum dots embedded in a short-circuited p–n junction to form photocurrent. The phenomenon cannot be explained by thermionic emission, tunneling process, and intermediate-band theories. A new mechanism is suggested that the photo carriers escape directly from the quantum dots to form photocurrent rather than relax to the ground state of quantum dots induced by a p–n junction. The finding is important for understanding the low-dimensional semiconductor physics and applications in solar cells and photodiode detectors.

InAs1–xSbx with different compositions is grown by molecular beam epitaxy on (100)-oriented semi-insulating GaAs substrates. The increase of Sb content in the epilayer results in the deterioration of crystal quality and surface morphology. Hall measurements show that the carrier concentration increases with the composition of Sb. The electron mobility decreases initially, when Sb composition exceeds a certain value, and the mobility increases slightly. In this work, we emphasize the comparison of crystal quality, surface morphology and electrical properties of epilayers with different Sb compositions.

Granular systems contain an internal force delay, which significantly influences their dynamical properties. Methods to estimate this delay in the presence of external disturbances are not systematically studied. Addressing this problem, we report the frequency response of a dense-fine-sand system to an external shear oscillator. With increasing frequency the mechanical spectrum measured shows four peaks of the energy dissipation, corresponding to four decreases of modulus. We discuss in detail the corresponding relationship between the loss peaks and the grain chains. The discussion indicates that the energy dissipation of the granular materials comes from two parts: the fragile dissipation and the rheological dissipation.