Grown by metalorganic vapour phase epitaxy (MOVPE) InxGa1−xAs metamorphic laser power converters have been considered. Metamorphic buffer designs with high quality top layers have been developed. ...Photovoltaic converters with In0.24Ga0.76As photoactive area and optimised buffer have demonstrated efficiency 41.4% for 1064 nm monochromatic radiation conversion and ∼40% for laser power conversion.
Photovoltaic laser-power converters for a wavelength of λ = 809 nm are developed and fabricated on the basis of single-junction AlGaAs/GaAs structures grown by metal-organic vapor-phase epitaxy. The ...parameters of the photovoltaic structure constituted by an optical “window” and a cladding layer are optimized by mathematical simulation. Photovoltaic converters with areas of
S
= 10.2 and 12.2 mm
2
and 4 cm
2
are fabricated and studied. For photocells with S = 10.2 mm
2
, the monochromatic efficiency (η) was 60% at a current density of 5.9 A/cm
2
. A photovoltaic module with a working voltage of 4 V (η = 56.3% at 0.34 A/cm
2
) is assembled.
Abstract
Epi-side down bonding on a silicon substrate of AlGaAs/GaAs microdisk lasers is presented. A heterostructure with coupled large optical cavities enables location of an InGaAs quantum dot ...active region at a distance of ∼1
µ
m from the heterostructure surface. The thermal resistance was reduced to 0.2 and 0.1 K mW
−1
for disks of 30 and 50
µ
m in diameter, respectively. The maximum continuous-wave power limited by the thermal rollover is more than doubled after bonding.
An option for the structural design of the metamorphic InGaAs photovoltaic converter is presented. The peculiarity of the proposed device is the ability to operate efficiently with the high-power ...1064 nm laser radiation at the elevated up to +125°C temperatures. The temperature dependencies of the output photovoltaic parameters for two types of InxGa1-xAs laser-power converters are presented in regard to In content: with x = 0.23 and x = 0.18 and with an efficiency of ∼50% and ∼40% (25 °C), respectively. For In0.18Ga0.82As device, an increase in efficiency of up to 50% is recorded upon transition to a temperature range of 50÷60 °C with maintaining efficiency at a level of more than 45% at elevated to 100 °C operating temperatures. In comparison, the "standard" In0.23Ga0.77As device performs a negative efficiency trend within a whole temperature range with absolute values below 45% in practically important operating modes of +75÷100 °C.
Hybrid quantum well-dots (QWD) nanostructures have been formed by deposition of 7-10 monolayers of In0.4Ga0.6As on a vicinal GaAs surface using metal-organic chemical vapor deposition. Transmission ...electron microscopy, photoluminescence and photocurrent analysis have shown that such structures represent quantum wells comprising three-dimensional (quantum dot-like) regions of two kinds. At least 20 QWD layers can be deposited defect-free providing high gain/absorption in the 0.9-1.1 spectral interval. Use of QWD media in a GaAs solar cell resulted in a photocurrent increment of 3.7 mA cm−2 for the terrestrial spectrum and by 4.1 mA cm−2 for the space spectrum. Diode lasers based on QWD emitting around 1.1 m revealed high saturated gain and low transparency current density of about 15 cm−1 and 37 A cm−2 per layer, respectively.
The polarization-resolved electroluminescence spectra of waveguide structures based on quantum well–dots are investigated in the temperature range of 60–300 K. It is found that the ground-state ...emission consists of two peaks with different degrees of TE polarization. The spectral separation of these peaks decreases with a decrease in temperature. The observed bimodality is attributed to the existence of two different types of objects in the active region, namely, quantum well–dots, whose emission is only partially TE polarized, and quantum dots, which emit nearly fully TE polarized light.
Spectroscopic reflectometry was used within 700-1600 nm wavelength range to investigate dispersion curves for In
Al
As, In
Al
Ga
As, and In
Ga
As layers, which constituted the purpose-made ...metamorphic InAlGaAs/GaAs Bragg reflector (BR). The procedure for determining the refractive index based on analyzing variations in cross-correlation coefficient obtained for reflection coefficient calculated and experimental dependences is presented. The sensitivity of the proposed method for variations in refractive index was investigated depending on the number of BR periods, the extinction coefficient of the layers of BR, and the wavelength range with respect to the main reflection maximum.
Investigation of IR light emitting diodes (wavelength 850 nm) based on AlGaAs/GaAs heterostructures with multiple quantum wells in the region generating radiation grown by the MOCVD technique has ...been carried out. Post-growth technologies for removing the substrate and for transfer the heterostructure on an alien carrier with an optical reflector have been developed. Technological regimes for fabricating the reflector have been optimized, and the increase of the IR radiation reflection coefficient up to 92–93% has been achieved. Light-emitting diodes with the external quantum efficiency 28.5% have been fabricated.
Expanding the photosensitivity spectrum of a single-junction GaAs-based solar cell to 1100 nm by using InGaAs hybrid quantum well dots (QWDs) multilayer media is reported. This nanostructure ...represents an In0.3Ga0.7As quantum wells with modulation of thickness and composition. Up to 15 QWD layers alternated with GaAs spacers can be inserted in an i-region of the GaAs p–i–n junction without impairing its crystal quality and quantum efficiency in spectral interval of GaAs absorption. The QWD layers are responsible for appearance of a longer wave spectral response (900–1100 nm). A photocurrent increment as high as 4.6 (5.2) mA/cm2 for terrestrial (space) spectrum is demonstrated.
The effect of positioning of the In
0.8
Ga
0.2
As quantum dots (QDs) array in the
i
-region of the solar cell (SC) on its photogenerated current and dark saturation currents, which determine the ...device operating voltage, have been investigated. It was found out that the indicated photoelectric characteristics depend on the location of the QD array relative to the electric field of the
p–n
junction. The displacement of the QD array to the boundary of the weakly doped base leads to a decrease in the photogenerated current. But at the same time, the voltage drop effect, which is well-known for nanoheterostructural SC, is minimal.
PDF
