A new type of thermally stable GaAs/AlGaAs tunnel diode with an intermediate i-layer is proposed as a connecting element between photoactive sub-elements in monolithic multijunction photoconverters. In the temperature range of (25-80) degrees C, the current-voltage p++-Al0.4Ga0.6As:(C) structures of connecting tunnel diodes were studied. The temperature dependences of the peak tunneling current density - (Jp) and differential resistance - (Rd) were obtained. In the samples of tunnel diodes of the structure with an i-layer, an order of magnitude higher Jp values and an order of magnitude lower Rd values were obtained, with higher temperature stability than in the samples of the structure without an i-layer. The results obtained are useful in the development and creation of monolithic multijunction photoconverters of high-power laser radiation.

The processes of heat removal from multijunction solar cells on a germanium substrate to AlN ceramics through a solder layer were studied by thermal wave photodeflection methods. Two types lead-free solder based on SnBi and SnAgCu were used under various pressure soldering conditions. The thermal conductivity and thermal resistance of the solder layers are compared. It is shown that the thermal conductivities of the solder layers differ from the reference data for the corresponding metal alloys, and in some cases may depend on the pressure during the brazing process.

Studies of microwave photovoltaic module made of AlGaAs/GaAs p-i-n photodiodes at conversion of laser radiation in the photovoltaic mode of operation have been carried out. Based on the obtained experimental characteristics, it is shown that the module, when excited by pulsed laser radiation with a duration ≤ 350 ps, at a wavelength of 780 nm, provides a photoresponse with full width at half maximum (FWHM) half-wave of bipolar pulses ~ 500 ps. Taking into account the experimental data, mathematical modeling shows that at the pulse duration of the input laser radiation 240ps the developed module is able to provide fast response with FWHM ≤ 280 ps.

A model of an autonomous receiving station of free space optical communication system based on a multi-section energy heterostructure (HJT) Si photoconverter and an information photodetector based on AlGaAs/GaAs p-i-n photodiodes has been developed. The energy part, when excited by laser radiation with a power of ~ 264 W at a wavelength of 0.974 μm in the photovoltaic mode, provided ≥ 60 W of electric power. The photodetector of the information channel, when excited by pulsed radiation at a wavelength of 0.78 μm, provides response time in the photovoltaic mode in the sub-nanosecond range. Keywords: free space opical communication, receiving station, HJT Si photoconverter, AlGaAs/GaAs p-i-n photodetector, laser radiation, pulsed radiation

This article attempts to assess the radiation resistance of heterostructure silicon solar cells to the effects of 1 MeV electrons and discusses their prospects for power supply of the global low-orbit satellite communication system. The data obtained from this study allow us to identify the most promising types of heterostructure silicon solar cells for use in low-orbit spacecraft. These are n-α-Si:H-(p)c-Si:Ga-p-α-Si:H and n-µc-Si:H-(p)c-Si:Ga-p-α-Si:H solar cells. The degradation in efficiency of these structures was less than 30

An AlGaAs/GaAs photovoltaic converter for a mock-up of an environmentally friendly radioisotope energy source of ultra-long use with a YPO4 : Eu/(238Pu) radioluminescent emitter with an extremely low content of the isotope 238Pu<0.1 wt.% was studied. The modeling of the Al0.8Ga0.2As/GaAs heterostructure for the conversion of nanowatt power levels of an optical signal has been carried out. The calculated and experimental efficiency of the mock-up with a photovoltaic converter at a radioluminescent source power of 1 nW was ~1.4%. Keywords: radioisotope energy source, AlGaAs/GaAs photo converter, optical radiation radioluminescent source, current flow mechanisms, conversion efficiency.

prudchenkokk@mail.ioffe.ru Abstract. The possibility of efficient conversion of continual infrared laser radiation by heterojunction technology a-Si:H/c-Si photovoltaic converters is demonstrated. The photo-voltaic characteristics of eight different types of heterojunction structures were investigated. The photovoltaic converters of the n-& alpha;-Si/n-c-Si/p-& alpha;-Si heterojunction structure with contact grid Ag turned out to be the best in terms of dark currents, external quantum efficiency, I-V characteristics, and conversion efficiency of laser radiation with 1064 nm wavelength at a pow-er density up to 2 kW/m2. The maximum efficiency-' 24.5% of this structure was reached at power density of 1 kW/m2.

A model of an autonomous receiving station of free space optical communication station based on a multi-section energy heterostructure (HJT) Si photoconverter and an information photodetector based on AlGaAs/GaAs p-i-n photodiodes has been developed. The energy part, when excited by laser radiation with a power of ~264W at a wavelength of 0.974µm in the photovoltaic mode, provided ≥60W of electric power. The photodetector of the information channel, when excited by pulsed radiation at a wavelength of 0.78µm, provides speed in the photovoltaic mode in the sub-nanosecond range.

The current-voltage characteristics of two types of GaAs-(delta Si)/i-(GaAs/Al0.2Ga 0.8As)/p++-Al0.2Ga0.8As-(delta Be) tunnel diode (TD) structures grown at different temperatures and epitaxial layer thicknesses have been investigated in the temperature range 100-400 K. Temperature dependences of the main TD parameters were determined: the peak value of the tunnel current density (Jp), the valley current density (Jv) and the differential resistance (Rd). TD samples of structure A grown at 500 degrees C exhibited the highest values of the peak current density (Jp <= 220 A/cm2) with temperature stability of 93 % over the whole temperature range. TD samples of structure B grown at 450 degrees C showed lower values of the peak tunneling current density (Jp <= 150 A/cm2), with significantly linear temperature dependence. Our findings can be used in the design and development of monolithic multijunction photoconverters of powerful laser radiation.

The radiation resistance of different types of heterostructural silicon solar cells under irradiation with 1 MeV electrons in the fluence range 2.5•1014 - 1•1015 cm-2 has been studied. Studies have shown that the smallest degradation of the“saturation” currents of the diffusion current flow mechanism from J0d ≤ 5 10-13 to J0d ≤ 3 10-12 A/cm2 and efficiency from 19.2 to 13.6% (AM0, 1367W/m2) were n-α-Si:H/c-p(Ga)/p-α-Si:H and n-µc-Si:H/c-p(Ga)/p-α-Si:H. The results obtained make it possible to evaluate the prospects for the use of heterostructure silicon solar cells for low-orbit spacecraft.

The possibility of efficient conversion of constant laser radiation using alpha-Si:H/c-Si structures in the transparency window of the Earth's atmosphere at wavelength 1.06 mu m is shown for the first time. A hybrid photovoltaic converter based on alpha-Si:H/c-Si cells and AlGaAs/GaAs photodetectors has been developed and manufactured. The photoelectric con-verter provides simultaneous conversion of radiation from two types of laser sources in the photovoltaic mode: continuous at a wavelength of 1.06 mu m with an efficiency of similar to 26% and pulsed at a wavelength of 0.78 mu m of <= 900 ps FWHM.

An AlGaAs/GaAs photovoltaic converter for a mock-up of an environmentally friendly radioisotope energy source of ultra-long use with a YPO4 :Eu/(238Pu) radioluminescent emitter with an extremely low content of the isotope 238Pu < 0.1 wt

The radiation resistance of different types of heterostructural silicon solar cells under irradiation with 1 MeV electrons in the fluence range 2.5 × 1014–1 × 1015 cm–2 has been studied. Studies have shown that the smallest degradation of the “saturation” currents of the diffusion current flow mechanism from J0d ≤ 5 × 10–13 to J0d ≤ 3 × 10–12 A/cm2 and efficiency from 19.2 to 13.6

The dark current–voltage characteristics of a p–n structure created on the surface of an n-type GaAs wafer by Ar+ ions with the energy Ei = 2500 eV are studied. To avoid the metallization of a thin (~10 nm) ion-modified p-type layer, multilayer metal contacts are deposited onto both sides of the plate without subsequent annealing. The diode effect with a forward-to-reverse current ratio up to three orders of magnitude is observed in the voltage range as high as 0.7 eV contrary to the unirradiated reference sample. The linear dependence of most current–voltage characteristics of the unirradiated reference sample and coincidence of the experimental current–voltage characteristics with the calculated ones for the ion-induced p–n-structure indicate the predominantly ohmic nature of the metallic contacts and that the observed diode effect is determined by the ion-induced p–n structure. An analysis of two regions with different slopes in the current–voltage characteristics reveals two current-transport mechanisms: recombination and diffusion. The considered effect of the ion-induced formation of the p–n structure limits the use of low-energy argon ions for preparing an atomically clean surface of n-type GaAs-based semiconductors for their study by surface-sensitive methods because the p–n structure is formed on the surface instead of a homogeneous material.

It is shown that the mesa architecture and the achieved quality of the side surfaces of the mesa structure of multijunction concentrator solar cells provide an increase in their efficiency up to 36.7% at a concentration ratio of up to 100× times (AM0; 0.136 W/cm2). The architecture of mesa structures with the subsequent separation of epitaxial wafers of monolithic InGaP/Ga(In)As/Ge nanoheterostructures into chips was carried out by the method of one-stage chemical etching in an HBr : H2O2 : H2O solution (8 : 1 : 100), through a photoresist mask to a depth of 12–18 μm. The conditions for one-stage etching are determined, which ensure the formation of a smooth and even mesa side surface of the InGaP/Ga(In)As/Ge nanoheterostructure containing layers of different composition and thickness. Determination of the activation energy showed that etching occurs in the diffusion region of the heterogeneous process. With an increase in the etchant temperature from 2 to 36°C, a change in the inclination angle in the region of the Ge substrate from 4.5° to 25° is observed, which makes it possible to optimize the number of concentrator solar cells and their quality during the final mechanical separation of the epitaxial wafer into chips.

An AlGaAs/GaAs photovoltaic converter for a mock-up of an environmentally friendly radioisotope energy source of ultra-long use with a YPO4:Eu/(238Pu) radioluminescent emitter with an extremely low content of the 238Pu isotope < 0.1 wt.% was studied. The modeling of the Al0.8Ga0.2As/GaAs heterostructure for the conversion of nanowatt power levels of an optical signal has been carried out. The calculated and experimental efficiency of the mock-up with a photovoltaic converter at a radioluminescent source power of 1nW was ~ 1.4%.

The processes of heat removal from multijunction solar cells on a germanium substrate to AlN ceramics through a solder layer were studied by thermal wave photodeflection methods. Two types lead-free solder based on SnBi and SnAgCu were used under various pressure soldering conditions. The thermal conductivity and thermal resistance of the solder layers are compared. It is shown that the thermal conductivities of the solder layers differ from the reference data for the corresponding metal alloys, and in some cases may depend on the pressure during the brazing process.

Misorientation characteristics of the optical system (submodule) including a hybrid solar cell, based on InGaP/Ga(In)As/Ge and Si cells integrated into a crystalline heat-removing silicon base and optical emission concentrators, linear Fresnel lenses and lateral reflectors have been studied. The optical system provides at a zero misorientation an electric power of 390 W/m(2) and up to 4 W/m(2) from the integrated Si cells. At a 24 degrees misorientation of the submodule along the focal line of the lens concentrator, the short-circuit photocurrent decreases by 15% relative to the maximum value, and at that in the orthogonal direction, across the focal line, the photocurrent decreases to 0.6 of its maximal value.

The problem is considered related to the accumulation of toxic metals in the body of employees in industries with unfavorable working conditions. The mechanism of accumulation of toxic metals over time in the body of employees of two facilities for solar modules production was studied. «Elemental portraits» of employees were compiled, demonstrating the redistribution of bioelements in the human body. The comparison is made concerning the «elemental portraits» of workers employed in the production of solar modules of different types: based on heterojunction silicon solar cells, and, on the basis of multijunction solar cells (using A3B5 compounds). A comprehensive study of the technological cycle of solar modules production was carried to identify the features of such enterprises. As a result of the workers hair study, a heterogeneous distribution of the content of vital and toxic elements was revealed. Thus, in the hair samples of employees of the enterprises under consideration, a statistically significant (p < 0.05) showed an increased level of toxic and conditionally toxic elements (aluminum, germanium, gallium, indium) relative to similar indicators in a group of practically healthy people. In addition, metabolic disorders, and a decrease in the level of such vital elements as zinc, magnesium and calcium were found. Based on the conducted analysis, it was found that «elemental portraits» can be used to develop and implement measures for improving working conditions and reducing occupational risks at the workplaces of the enterprises with unfavorable working conditions, in particular, for the solar modules production.

Characteristics of double-cascade nonmonolithic p-i-n AlGaAs/GaAs photovoltaic converters of high-power laser radiation, electrically combined with n++-GaAs/i-GaAs/i-AlGaAs/p++-AlGaAs tunnel diodes, have been studied. The AlGaAs/GaAs p-i-n structures of the photovoltaic converters and n++-GaAs/i-GaAs/i-AlGaAs/p++-AlGaAs tunnel diodes were grown by molecular-beam epitaxy. The photoelectric characteristics of the double-cascade AlGaAs/GaAs photovoltaic converters were examined in the temperature range from 103 to 298 K under excitation with a laser light wavelength of 809 nm and a power density ⩽92 W/cm2. The double-cascade p-i-n AlGaAs/GaAs nonmonolithic photovoltaic converters of planar design had a fill factor of 0.88 and efficiency of 58.2% at a temperature of 103 K. It was shown experimentally that the current-voltage characteristics of the connecting n++-GaAs/i-GaAs/i-AlGaAs/p++-AlGaAs tunnel diodes affect the photoelectric parameters of the double-cascade photovoltaic converters of high-power laser light.