Низкотемпературная фотолюминесценция монослоя WSe-=SUB=-2-=/SUB=-, полученного механическим слоением с использованием золота

We studied the optical properties of an atomically thin WSe$_2$ film obtained by gold-assisted mechanical exfoliation. Raman scattering spectra, low-temperature photoluminescence, and micro-reflection from large-scale monolayer are investigated. At room temperature, the optical properties of such a film reproduce the properties of WSe$_2$ monolayers obtained by regular mechanical exfoliation. It is shown that at low temperatures, the radiation spectra of the resulting film are determined by standard mechanisms of radiative recombination involving free excitons, bound excitons, and trions. However, in contrast to room temperatures, there is a significant difference in the spectral width and intensity of the lines compared to monolayers WSe$_2$, obtained regular way from the same source material. The differences found, demonstrating a significant increase in background doping and structural disorder when using gold-assisted exfoliation, may be meaningful for a number of optoelectronic applications of atomically thin WSe$_2$ films.

Study of the Cross-Influence between III-V and IV Elements Deposited in the Same MOVPE Growth Chamber

We have deposited Ge, SiGe, SiGeSn, AlAs, GaAs, InGaP and InGaAs based structures in the same metalorganic vapor phase epitaxy (MOVPE) growth chamber, in order to study the effect of the cross influence between groups IV and III-V elements on the growth rate, background doping and morphology. It is shown that by adopting an innovative design of the MOVPE growth chamber and proper growth condition, the IV elements growth rate penalization due to As “carry over” can be eliminated and the background doping level in both IV and III-V semiconductors can be drastically reduced. In the temperature range 748–888 K, Ge and SiGe morphologies do not degrade when the semiconductors are grown in a III-V-contaminated MOVPE growth chamber. Critical morphology aspects have been identified for SiGeSn and III-Vs, when the MOVPE deposition takes place, respectively, in a As or Sn-contaminated MOVPE growth chamber. III-Vs morphologies are influenced by substrate type and orientation. The results are promising in view of the monolithic integration of group-IV with III-V compounds in multi-junction solar cells.

Influence of Lateral Straggling of Implated Aluminum Ions on High Voltage 4H-SiC Device Edge Termination Design

This paper presents the analysis of Aluminum profile implanted into 4H-SiC with low background doping concentration. A strong lateral straggling effect was discovered with secondary electron potential contrast (SEPC) method, and analyzed by Sentaurus Monto Carlo simulations. The effect of lateral straggling was included in the edge termination design using Sentaurus TCAD simulation tool, and the results are compared with design not including the lateral straggling effect. The effect of interface charge on the electric field distribution and breakdown voltage of different 10 kV device edge termination designs was compared and analyzed.