Study of the effect of bismuth electrophysical properties of gallium phosphide single crystals

Semeconductor compounds with is ovalent impurities, effect of bismuth electrophysical properties, processing into a growing crystal, electrical properties of Ga P, mobility of crystals , the interaction of bismuth with silicon

is the absorption of solar radiation in semiconductor materials and the resulting potential barriers of charge pairs formed in the semiconductor. based on the processes of separation and transmission to an external electrical circuit.
Its electrical parameters are measured under normal lighting conditions (approximately the width of Tashkent corresponds to the dawn of a hot spring day). Photocells and solar cells are characterized by the production technology of the maximum output power, operating and maximum voltages, currents, efficiency of conversion of light energy into electricity. The use of solar energy is achieved by converting light into electricity using photocells -solar cells. Japan, Germany and the United States are leading in this regard. Generating heat energy using solar collectors -solar furnaces -the surface area of solar furnaces is measured by 21 million square meters. Japan, Israel and Greece are in the lead in this regard. Today, solar photovoltaic plants and collectors of solar water heating are successfully used in Surkhandarya, Jizzakh, Bukhara, Navoi, Tashkent, Andijan regions and the Republic of Karakalpakstan. As a result of fundamental research in the early period, it was found that the complete absorption of the spectrum of solar radiation depends on the properties of the material. It was found that the formation of charge pairs of absorbed radiation in the volume of the material and the process of their separation depends on the potential barrier (n -p transition) formed inside the semiconductor material and the properties of the material. This allowed to optimize the parameters of solar cells. Practical research includes the design and manufacture of QE structures with optimal parameters, the study of their properties, the development of technology of QE, batteries and photovoltaic devices, based on which different designs, operating in different conditions, Dedicated to the production of power supply systems for consumers of different capacities. Modern QE is made of different semiconductor materials, depending on the conditions under which it is used (in space, on Earth, in direct -direct solar radiation, concentrated solar radiation, in extreme cases, etc.). Most of the QE currently produced and used as a source of electricity for human consumption is made of silicon. The main reason for this is that silicon is the basis of microelectronic devices, which are widely used in modern economy. Second, silicon is an elemental semiconductor, which makes up about 30% of the Earth's composition, as well as the development of technology. Currently, with the advent of solar-based semiconductor silicon compounds, the demand for semiconductor devices based on these compounds is growing. One of the main tasks is to study the electrophysical properties of each solar cell and create new devices based on them. Solar elements are semiconductor materials that work on and convert solar energy. The advent of semiconductor devices based on sunlight has led to low-cost, high-performance diode structures. Solar elements can consist of a semiconductor element, heterostructures with atoms of semiconductor compounds or many elements. Depending on the structure, the physical characteristics vary. Characteristics of the crystals that make up the elements of the sun include the intensity of light, the visible type of wavelength, the intensity of radiation. Omlik contacts of light crystals are made on the basis of skirt film technology. With the structure of solar elements from heterostructures, the efficiency of space efficiency is increasing. The main method of growing semiconductor heterostructures based on solar elements is the method of hydride epitaxy, and structures grown in this way have a great potential for use in space.
Doping with bismuth does not introduce additional hardware and technological changes in the process of growing GaP <Bi> single crystals. It was only required to select the required amount of bismuth added to the charge to reduce the evaporation of volatile components.
The chamber was filled with argon until a pressure of 6x106 Pa was reached (after heating the setup), after which high-frequency heating was switched on until the flux was completely melted, and then, while the crucible was rotating at a certain speed for homogenization, the charge. The starting material was polycrystalline gallium phosphide with bismuth additives in an amount of 0.00 to 0.05 mol% [3].
Study of the content of bismuth in gallium phosphide made it possible to establish that the solubility of Bi in GaP is very low (less than 10-5 mol.%). If we assume that Bi in GaP is in the phosphide substitution position, then it is not an electroactive impurity.
With the introduction of Bi more than 0.05 mol%, the precipitation of the second phase was observed in the obtained crystals, and at a low content (<0.01 mol%), no effect on the electrical properties of GaP was found.
The electrophysical characteristics of GaP <Bi> single crystals were studied by the van der Pauve method, i.e. studied the effect of bismuth on the concentration and mobility of charge carriers in gallium phosphide. GaP single crystals obtained from the melt and containing bismuth in the indicated concentration range had [4] the mobility on average 40% higher than that of undoped crystals (Table).
Mass spectrometric analysis with a spark source showed that in GaP polycrystals the silicon content was 2x10-3 at%, and in GaP single crystals <Bi> in the upper part 2x10-5 at% and in the lower part 9x10-6 at% silicon. The bismuth content was less than 10-5 at%. Apparently, an increase in the mobility in GaP <Bi> crystals is associated with a strong decrease in the silicon content. In this case, bismuth does not introduce any additional energy levels into the band gap of gallium phosphide.
The interaction of bismuth with silicon leads to a decrease in the distribution coefficient of silicon, as a result of which a smaller amount of this impurity gets into the growing crystal. The interaction of bismuth and residual silicon atoms can also occur in the solid phase. In this case, the crystal is "purified" due to the formation of stable associated complexes of atoms, facilitating the transition of residual impurities into an inactive state.
3. CONCLUSION The effect of doping with bismuth on the electrophysical properties of gallium phosphide has been studied. It is shown that an increase in the bismuth content from 0.01 to 0.05 mol.% In the initial melt leads to a decrease in the carrier concentration and an increase in the mobility, as well as to a decrease in the concentration of residual silicon in single crystals.