Local triboelectrification of an n-GaAs surface using the tip of an atomic-force microscope

The method of scanning Kelvin-probe microscopy is used to show that the effect of triboelectrification is observed when the tip of an atomic-force microscope interacts with the surface of n-GaAs epitaxial layers. The sign of the change in the potential indicates that the sample surface after triboelectrification becomes more negative. The observed specific features of the phenomena can be attributed to the thermally activated generation of point defects in the vicinity of the sample surface due to deformation caused by the tip.     

Anomalies in Photovoltaic Characteristics of Multijunction Solar Cells at Ultrahigh Solar Light Concentrations

Technical Physics Letters - An anomaly appearing in the photovoltaic characteristics of triple-junction GaInP/GaAs/Ge and of the corresponding double-junction GaInP/GaAs solar cells at...     

Capacitive Characteristics of High-Speed Photovoltaic Converters at Combined Lighting

Semiconductors - p–i–n GaAs photovoltaic converters of modulated laser radiation (810–830 nm) transferring both energy (laser power) and information signal were developed. The...     

Effects of Doping of Bragg Reflector Layers on the Electrical Characteristics of InGaAs/GaAs Metamorphic Photovoltaic Converters

Semiconductors - The current–voltage characteristics of InxGa1 –xAs/GaAs metamorphic photovoltaic converters with built-in n-InGaAs/InAlAs Bragg reflectors are studied at an indium...     

Comparative Analysis of the Optical and Physical Properties of InAs and In0.8Ga0.2As Quantum Dots and Solar Cells Based on them

Semiconductors - InAs and In0.8Ga0.2As quantum dots in a GaAs matrix as well as GaAs solar cells with quantum dots of both types in the i-region are obtained by metalorganic vapor-phase epitaxy. As...     

Optical properties of hybrid quantum-confined structures with high absorbance

The methods of photoluminescence and photoconductivity spectroscopy and the spectroscopy of photocurrent of a p–i–n structure are used to study samples with hybrid quantum-confined medium “quantum well–dots” (QWD) structures grown on GaAs substrates. The significant contribution of QWD states, which extends the GaAs absorption range to 1075 nm, is found in the photoconductivity and photocurrent spectra. The absorption and luminescence of the quantum-confined structures possess characteristic features of quantum wells. Analysis of the photocurrent and photoconductivity spectra demonstrate that the excitation of carriers from localized QWD states has a combined nature: at temperatures lower than 100 K and an electric-field strength of below 40 kV/cm, excitation is possible via tunneling to the matrix, while at higher temperatures thermal activation coming into play. Also, lateral photoconductivity is observed in the layers of quantum-confined structures.     

In<Subscript>0.8</Subscript>Ga<Subscript>0.2</Subscript>As Quantum Dots for GaAs Solar Cells: Metal-Organic Vapor-Phase Epitaxy Growth Peculiarities and Properties

The growth peculiarities of In_0.8Ga_0.2As quantum dots and their arrays on GaAs surface by metalorganic vapor-phase epitaxy are investigated. The bimodal size distribution of In_0.8Ga_0.2As quantum dots is established from the photoluminescence spectra recorded at different temperatures. The growth parameters were determined at which the stacking of 20 In_0.8Ga_0.2As quantum-dot layers in the active area of a GaAs solar cell makes it possible to enhance the photogenerated current by 0.97 and 0.77 mA/cm² for space and terrestrial solar spectra, respectively, with the high quality of the p–n junction retained. The photogenerated current in a solar cell with quantum dots is higher than in the reference GaAs structure by ~1% with regard to nonradiative-recombination loss originating from stresses induced by the quantum-dot array.     

Counteracting the Photovoltaic Effect in the Top Intergenerator Part of GaInP/GaAs/Ge Solar Cells

Semiconductors - The “top” intergenerator part situated between the GaInP and GaAs subcells (electric power generators) is analyzed. The shape of the light current–voltage...     

Optimization of structural and growth parameters of metamorphic InGaAs photovoltaic converters grown by MOCVD

Metamorphic Ga_0.76In_0.24As heterostructures for photovoltaic converters are grown by the MOCVD (metal–organic chemical vapor deposition) technique. It is found that, due to the valence-band offset at the p-In_0.24Al_0.76As/p-In_0.24Ga_0.76As (wide-gap window/emitter) heterointerface, a potential barrier for holes arises as a result of a low carrier concentration in the wide-gap material. The use of an InAlGaAs solid solution with an Al content lower than 40% makes it possible to raise the hole concentration in the widegap window up ~9 × 10¹⁸ cm^–3 and completely remove the potential barrier, thereby reducing the series resistance of the device. The parameters of an GaInAs metamorphic buffer layer with a stepwise In content profile are calculated and its epitaxial growth conditions are optimized, which improves carrier collection from the n-GaInAs base region and provides a quantum efficiency of 83% at a wavelength of 1064 nm. Optimization of the metamorphic heterostructure of the photovoltaic converter results in that its conversion efficiency for laser light with a wavelength of 1064 nm is 38.5%.