Process and device simulations aimed at improving the emitter region performance of silicon PERC solar cells

Achieved levels of Silicon-based passivated emitter and rear cell (PERC) solar cells' laboratory and module-level conversion efficiencies are still far from the theoretically achievable Auger limit of 29.4% for silicon solar cells, prominently due to emitter recombination and resistive losses. The emitter region in PERC devices is formed by using either ion implantation followed by a diffusion process or POCl3 diffusion. In ion-implanted emitter-based PERC, the process variables such as dose, energy, diffusion time, and temperature play a vital role in defining the characteristics of the emitter region. Detailed investigation of these parameters could provide a pathway to mitigate the recombination as well as resistive losses; however, it requires a considerable budget to optimize these parameters through a purely experimental approach. Therefore, advanced industrial standard process and device simulation are perceived in this work to carry out the comprehensive study of process variables. Investigation of ion implantation and diffusion process parameters on the PV performance of an upright pyramid textured, industrial standard stacked dielectric passivated PERC solar cell is carried out to deliver 22.8% conversion efficiency with improved PV parameters such as short circuit current density (JSC) of 40.8 mA/cm2, open-circuit voltage (VOC) of 686 mV, and fill-factor (FF) of 81.54% at optimized implantation and diffusion parameters, such as implantation dose of 5×1015 cm-2 with energy 30 keV followed 950 oC diffusion temperature and 30 min of diffusion time. The performance of the optimized PERC device is compared with already published large area screen printed contact-based device. This work may open up a window for the experimental work to understand the influence of process parameters on the emitter region to develop the highly efficient PERC solar cell in the future.

Temperature Characterization of Unipolar-Doped Electroluminescence in Vertical GaN/AlN Heterostructures

An electroluminescence (EL) phenomenon in unipolar-doped GaN/AlN/GaN double-barrier heterostructures—without any p-type contacts—was investigated from 4.2 K to 300 K. In the range of 200–300 K, the extracted peak photon energies agree with the Monemar formula. In the range of 30 to 200 K, the photon energies are consistent with A-exciton emission. At 4.2 K, the exciton type likely transforms into B-exciton. These studies confirm that the EL emission comes from a cross-bandgap (or band-to-band) electron-hole radiative recombination and is excitonic. The excitons are formed by the holes generated through interband tunneling and the electrons injected into the GaN emitter region of the GaN/AlN heterostructure devices.

Principles of synergetics in training of specialists physical and technical profile

The article discusses the use of the basic principles of synergetics in the training of physicists in the study of the discipline «Physical Electronics». The work is based on many years of experience in teaching the discipline at the Department of Radiophysics and Electronics of Karaganda State University named after E.A. Buketova. It is shown that the system «semiconductor structure + external source of electrical energy» can be considered as an open nonequilibrium thermodynamic system in which cooperative processes of spontaneous self-organization due to the constant exchange of energy and matter develop. The physical processes in bipolar transistors in the active mode of operation are analyzed. By means of a qualitative theoreti- cal analysis, it was established that the system under consideration interacts with self-organizing processes that result in spontaneous lowering of the potential barrier in the emitter region and an increase in similar barter in the region of collector junctions; spontaneous injection of minority charge carriers into the base is observed, resulting in a spontaneous increase in the concentration of minority charge carriers in the base layer adjacent to the transition. Spontaneous transfer of charge carriers through the base to the collector causes a spontaneous decrease in the collector junction resistance to the resistance of a forward-biased emitter junction, etc. All of the above processes determine the spontaneous redistribution of the voltage of the power source, as a result of which the power at the output of the transistor begins to exceed the power at its input, i.e. A bipolar transistor will amplify the power.

Mechanism research of negative resistance oscillations characteristics of the silicon magnetic sensitive transistor with long base region

A silicon magnetic sensitive transistor (SMST) with the negative resistance oscillation phenomenon is presented in this paper. The SMST of cubic structure is composed of three regions and three electrodes (E, C and B). Two of the regions (collector region and base region) are designed on the top surface of the SMST, and the emitter region is designed at the bottom of the SMST. Using microelectromechanical system (MEMS) technology, the chip is fabricated on [Formula: see text] orientation p-type silicon (near intrinsic) wafer and packaged on printed circuit board (PCB). When collector voltage (V[Formula: see text]) and the base injecting current (I[Formula: see text]) are a certain value, the experimental results show that the collector current (I[Formula: see text]) attains negative resistance oscillation phenomenon and it is influenced by the external magnetic field (B) and temperature (T). Based on the effect of deep-level impurities on the carrier net recombination rate, theoretical analysis demonstrates that the deep-level impurities are the main factors of the appearance for oscillations phenomenon.

Current Gain Degradation in 4H-SiC Power BJTs

SiC BJTs are very attractive for high power application, but long term stability is still problematic and it could prohibit commercial production of these devices. The aim of this paper is to investigate the current gain degradation in BJTs with no significant degradation of the on-resistance. Electrical measurements and simulations have been used to characterize the behavior of the BJT during the stress test. Current gain degradation occurs, the gain drops from 58 before stress to 43 after 40 hours, and, moreover, the knee current shows fluctuations in its value during the first 20 hours. Current gain degradation has been attributed to increased interface traps or reduced lifetime in the base-emitter region or small stacking faults in the base-emitter region, while fluctuations of the knee current might be due to stacking faults in the collector region.