CS241340B1 - Device for optical excitation of charge carriers - Google Patents

Abstract

The invention relates to the field of instrumentation for spectroscopy of deep trapping centers in solids. The device is intended for excitation of free charge carriers in solids, especially in semiconductors, in a cryostat, by optical means. The purpose of the invention is the possibility of its use in a cryostat without a vacuum pumping system while simultaneously increasing the efficiency of excitation of optical radiation and its transfer to the sample space in the cryostat. The stated purpose can be achieved by providing the cryostat closure with an opening at the sample storage location, through which the light guide of the semiconductor radiation source is guided. The radiation source is mounted on a radiator. A thermal shield made of thermal-insulating material is placed between the cryostat closure and the radiator. The invention can be used in the field of research and production of solids, especially semiconductors.

Description

4 241340

BACKGROUND OF THE INVENTION The present invention relates to cryptoids for the exacerbation of charge carriers of Streptophysiology. It belongs to the field of characterization of treated substances, especially semiconductors in the physics of electronics. In characterizing solids, it is in some cases necessary to investigate their properties under the influence of incident optical radiation over a wide temperature interval. In the field of semiconductor characterization, for example, the ODLTS - Opti-Deep-Level Transient Spectroscopy method is used, where the sample is irradiated by optical radiation, thus free charge carriers are excited in the area of the material under investigation.

The characterization is based on the analysis of physical relaxation processes after the end of irradiation in a wide temperature interval, usually 77 to 450 K. Divergent modifications of the ODLTS method are used, and hence the energy of the radiation in the energy bandwidth of the forbidden band Eg semiconductor , or with an energy less than that of Eg. For this purpose, cryostats are constructed with an optical radiation source. Semiconductor diodes, alasers, gas lasers, or a wide-spectrum filter with a desired wavelength filter may be used as the optical source. Cryostats have a vacuum pumping system and are provided with a window to allow irradiation of specimens placed in the cryostate. Furthermore, a cryostat solution is known which does not require the use of a vacuum pump system where the freezing of the water vapor at temperatures below 273 K occurs on the cap of the cryostat, which is the coldest spot in the sample.

So far, there is no known device enabling optical excitation of charge carriers in this type of cryostat. The known solutions employ a window cryostat and require a vacuum pumping system which imposes increased demands on the design and operation of such devices. Due to radiation losses, it is necessary to use optical sources with sufficiently high radiant power, in particular continuous-mode semiconductor lasers. Frequently used gas lasers have the disadvantage of the need for mechanical light pulse modulation.

The above disadvantages are substantially removed by the optical excitation device of the charge carrier according to the invention, the principle of which is that the cryostat closure is provided with an opening through which the light guide of the semiconductor radiation source is guided. The radiation source is attached to the radiator. Between the cryostat closure and the heat sink there is a thermal shielding of the thermo-insulating material.

By the invention it is possible to realize an economical and efficient device for optical excitation of charge carriers in cryostate. The placement of a ductile heat-cooler with a suitable medium required by the cryostat, for example by liquid vapor or vapor, makes it possible to utilize higher quantum efficiency at this temperature.

The small distance of the radiation source from the sample and the use of a suitable light guide ensures low loss of conduction radiation. This makes it possible to use LEDs as a radiation source, in addition to conductor lasers, despite less radiant power. By symmetrically positioning two semiconductor radiation sources with different wavelengths -m λ, λζ corresponding to the frequencies vi, v2 emitted by the radiating radiating conditions hi i i> Eg, h v2 <Eg on the condensers by irradiating the radiation in the cryo-state cap at the storage locations samples and temperature sensors can be used by one device to modify the ODLTS method by simply rotating the cryostat cap by> 180 °.

In the accompanying drawing, FIG. 1 shows a front view, FIG. 2 shows a plan view and FIG. 3 shows a cross-section of the proposed solution. ‘The cryostat closure 1 is a metal block, in the pattern there are 2, 2 vzorku for the sample and temperature sensors. The selections 2, 2 ‘are provided with openings through which samples and sensors are passed through the light guides 3, 3. The 4, 4 ič semiconductor radiation sources are mounted in coolers 5, 5 ‘. Between the cryostat closure 1 and the coolers 5, 5 &apos; there are rollers 7, 7 &apos; of thermally insulating material, of which the light guides 3, 3 &apos;

The closure 1 according to the invention closes the cryostat with a screw 8. Coolers S, 5 ‘se and coolant. Through the inlets 9, 9 *, electrical impulses are introduced into the source of radiation, whose light guide opens in the sample space 2. During the pulses of the semiconductor source 4, it emits radiation that is led through the light guide 3 passing through the opening of the cryostat 1 and impinges on the sample located in the cryostat space 2.

Both versions of the ODLTS method are achieved by rotating the DL-cryostat closure 180 ° and engaging the electrical leads 9 k leading to the second radiation source 4 4 with the desired desired wavelength emitted wavelength.

The invention can be used to investigate the properties of substances, especially solid fluxes, under the influence of incident optical radiation in the spectral range covered by semiconductor radiation sources in a wide temperature range. It is mainly ο> the field of manufacturing apparatus and equipment for characterizing semiconductor materials and components.

Claims (2)

5 6 241 3 4 0 OBJECT An apparatus for optical excitation of charge carriers in a cryostat, characterized in that the cryostat closure (1) is provided at the sample location (2) with an opening through which a light guide (3) of a semiconductor source (4) mounted in the radiator is guided. (5), wherein a thermal shield (6) is provided between the cryostat closure (1) and the radiator (5). VYNALEZU 2. Apparatus according to claim 1, characterized in that the cryostat closure (1) is provided at the symmetrical locations (2, 2 &apos;) of the temperature reader sample with openings through which the light guides (3, 3 &apos; (4, 4 &apos;) radiation sources attached to the coolers (5, 5 &apos;), wherein a thermal shield (6) is positioned between the closure (1) (cryostat and coolers (5, 5 &apos;).