Enhanced absorption process in the thin active region of GaAs based p-i-n structure

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, Ga As 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.

Characteristic improvements of thin film AlGaInP red light emitting diodes on a metallic substrate

We report a type of thin film Al Ga In P red light emitting diode（RLED） on a metallic substrate by electroplating copper（Cu） to eliminate the absorption of Ga As grown substrate.The fabrication of the thin film RLED is presented in detail.Almost no degradations of epilayers properties are observed after this substrate transferred process.Photoluminescence and electroluminescence are measured to investigate the luminous characteristics.The thin film RLED shows a significant enhancement of light output power（LOP） by improving the injection efficiency and light extraction efficiency compared with the reference RLED on the Ga As parent substrate.The LOPs are specifically enhanced by 73.5% and 142% at typical injections of 2 A/cm^2 and 35 A/cm^2 respectively from electroluminescence.Moreover,reduced forward voltages,stable peak wavelengths and full widths at half maximum are obtained with the injected current increasing.These characteristic improvements are due to the Cu substrate with great current spreading and the back reflection by bottom electrodes.The substrate transferred technology based on electroplating provides an optional way to prepare high-performance optoelectronic devices,especially for thin film types.

Effect of Dopant Concentration in a Base Layer on Photocurrent–Voltage Characteristics of Photovoltaic Power Converters

It is known that the p–n junction of an absorption region is a crucial part for power conversion efficiency of photovoltaic power converters.We fabricate four samples with different dopant concentrations in base layers.The dependences of power conversion efficiency and fill factor on input power are displayed by photocurrent–voltage measurement.Photoluminescence characteristics under open circuit and connected circuit conditions are also studied.It is found that the status of p–n junction matching is the critical factor in affecting the power conversion efficiency.In addition,series resistance of photovoltaic power converters impairs the efficiency especially at high input powers.Both the key factors need to be considered to obtain high efficiency,and this work provides promising guidance on designing photovoltaic power converters.