Vítězslav Benda

Deep energy levels in power diodes introduced by iridium diffusion

Abstract The results of a study carried out on N-type silicon and P + PNN + silicon diodes diffused with iridium at temperatures ranging from 820 to 940°C are reported. The iridium-related deep energy levels were measured using DLTS method. The energy levels E c = 0.16, 0.28 and 0.54 eV were found, the dominant recombination centre is of energy E c − 0.28 eV. Besides the energy levels, the influence of iridium diffusion on carrier lifetime and basic parameters of the diode structures was studied. It was found that iridium diffusion may be used successfully for the fabrication of fast, soft reverse recovery power diodes.

OCVD Carrier Lifetime in P+NN+ Diode Structures With Axial Carrier Lifetime Gradient

Abstract The OCVD (open circuit voltage decay) method is the generally used method for the determining of carrier lifetime in the structures of semiconductor devices. This paper is focused on power diode (P + NN + ) structures, in which is realised a carrier lifetime gradient to influence the current and voltage waveforms during the reverse recovery process. A theoretical analysis of the general features of voltage decay courses in OCVD measurements on diode structures with an axial carrier lifetime gradient in the diode base is presented. Some results obtained from both simulations and experimental measurements are discussed in the paper.

Improving of large-area GTO homogeneity by electron irradiation

Abstract For a reliable function of high-power GTOs it is important that individual parallel-connected segments of a GTO structure are nearly of the same characteristics, both static and dynamic. The presented paper deals with the study of electron irradiation influencing the carrier lifetime and decreasing the relative dispersion of the carrier lifetime on the area of power GTO. Theoretical presumptions were experimentally verified by measuring of current gain distribution in large-area GTOs before and after different electron irradiation doses.

A note on irradiance dependence of photovoltaic cell and module parameters

This paper provides an analysis of the irradiance influence on photovoltaic cell efficiency in dependence on the cell construction, using the standard equivalent circuit describing solar cell. The influence of the series resistance is discussed in details and results of simulations are completed with experimental result obtained by measuring crystalline silicon solar cells and in broad intervals of irradiance and temperature and measuring different types of PV modules in a broad interval of irradiance.

A simple method of in-process checking of the large area GTO homogeneity

Abstract For reliable function of GTO thyristors it is important that the parallel-connected segments of a GTO thyristor structure have similar characteristics, both static and dynamic. This paper deals with the study of homogeneity of large-area GTOs by measuring the current gain distribution over the GTO structure. The local current gain in an individual N + -emitter segment of a large area GTO may be evaluated from the reverse current induced by a positive gate signal at the reverse biased thyristor structure, and measurements on all segments of a GTO structure under conditions of a constant gate current and a constant anode voltage. This enables us to evaluate the large area GTO homogeneity with respect to the low injection carrier lifetime. Equipment developed enables us to obtain the current gain distribution in a short time.

Photovoltaics: The Basics

Abstract The aim of this chapter is to present and explain basic issues relating to principles of photovoltaics (PVs), from interaction of light with materials, processes of carrier generation and recombination to PV effect and basic characteristics of PV cells. The influence of irradiance and temperature on I–V characteristics is discussed, including problems of in-series and in-parallel connection of cells. Furthermore, principles of solar cell construction, PV cell efficiency limits are discussed along with losses in real PV cell structures. Finally, PV module construction, I–V characteristics, and PV module’s optical, thermal, and mechanical properties are discussed.

Crystalline Silicon Solar Cell and Module Technology

Abstract For more than 50 years, photovoltaic (PV) technology has seen continuous improvements. Yearly growth rates in the last decade (2007–16) were on an average higher than 40%, and the global cumulative PV power installed reached 320 GW p in 2016 and the PV power installed in 2016 was greater than 80 GW p . The workhorse of present PVs is crystalline silicon (c-Si) technology; it covers more than 93% of present production, as processes have been optimized and costs consistently lowered. The aim of this chapter is to present and explain the basic issues relating to the construction and manufacturing of PV cells and modules from c-Si. This includes the basic principles of manufacturing c-Si wafers (preparing pure silicon, fabrication of both single-crystal and multicrystalline ingots, and wafering), and the fabrication of c-Si PV cells and modules. This includes discussions on new designs and technologies that have resulted in increased efficiencies and decreasing production costs. Furthermore, the differences between technologies are discussed together with an explanation of the present domination of c-Si technology.

ANNEALING OF POLYCRYSTALLINE THIN FILM SILICON SOLAR CELLS IN WATER VAPOUR AT SUB-ATMOSPHERIC PRESSURES

Thin film polycrystalline silicon (poly-Si) solar cells were annealed in water vapour at pressures below atmospheric pressure. PN junction of the sample was contacted by measuring probes directly in the pressure chamber filled with steam during passivation. Suns-VOC method and a Lock-in detector were used to monitor an effect of water vapour to VOC of the solar cell during whole passivation process (in-situ). Tested temperature of the sample (55°C – 110°C) was constant during the procedure. Open-circuit voltage of a solar cell at these temperatures is lower than at room temperature. Nevertheless, voltage response of the solar cell to the light flash used during Suns-VOC measurements was good observable. Temperature dependences for multicrystalline wafer-based and polycrystalline thin film solar cells were measured and compared. While no significant improvement of thin film poly-Si solar cell parameters by annealing in water vapour at under-atmospheric pressures was observed up to now, in-situ observation proved required sensitivity to changing VOC at elevated temperatures during the process.

Electrical parameters of c-Si and CIS photovoltaic cells in dependence on temperature and irradiance

For photovoltaic applications, the knowledge about system behaviour in real operating conditions is desirable. Presented paper describes the dependences of all important parameters of crystalline silicon (c-Si) cell and CIS photovoltaic mini-module on both temperature and irradiance obtained using cell tester Pasan IIc.

Monitoring of carrier lifetime distribution in high power semiconductor device technology

Non-uniform distribution of carrier lifetime over the area of power bipolar semiconductor devices results in a non-uniform distribution of on-state current density and switching loses. Consequently, it results in non-uniform temperature distribution which can negatively influence the device reliability. Several methods can be used for measuring carrier lifetime distribution both in starting single crystal material and in device structures after high-temperature processes. Advantages and disadvantages of individual methods and an optimum area of applications are discussed in this paper. This paper is mostly oriented on a possibility to use LBIC method for measuring carrier lifetime distribution in the bulk of high voltage large-area devices, especially N^+NPP^+ diode structures.