Pure edge 90° misfit dislocations (MDs) are the most effective linear defects that combine the substrate and the film with different lattice parameters. A system consisting of a nonstressed film and a substrate approaches the perfect case in terms of the structural transition from one lattice parameter to the other if imperfections in the form of an ordered network of edge MDs are located exclusively at the interface, while threading dislocations are practically absent. The path to this perfect case goes through studying the possibilities of creating such an ordered network of edge MDs. The mechanism of formation of edge MDs proposed previously by Kvam et al (1990 J. Mater. Res. 5 1900) is discussed. This mechanism involves induced formation of a complementary pair of 60° MDs whose coalescence at the interface creates an edge MD. Some publications are presented, which demonstrate on the basis of experimental data that this mechanism under certain conditions c...

For maximum fibre-coupled power, high power broad area diode lasers must operate with small lateral far field angles at high continuous wave (CW) powers. However, these structures are laterally multi-moded, with low beam quality and wide emission angles. In order to experimentally determine the origin of the low beam quality, spectrally resolved near and far field measurements were performed for a diode laser with 50 µm stripe width. Within the range measured (CW optical output powers to 1.5 W) the laser is shown to operate in just six stable lateral modes, with spatially periodic profiles. Comparisons of the measured profiles with the results of two-dimensional modal simulation demonstrate that current-induced thermal lensing dominates the lateral waveguiding, in spite of the presence of both strong built-in index guiding and gain guiding. No evidence is seen for filamentation. Building on the diagnosis, proposals are presented for improvements to beam quality.

Direct detection thin-film bipolar narrow-gap Hg _{1− x}Cd _x Te semiconductor is considered as a waveguide THz/sub-THz bolometer. The response of such thin layer detectors was calculated and measured in the ν = 0.037–1.54 THz frequency range at T ∼ 70–300 K. Noise equivalent power of such detectors can reach NEP _{300 K} ∼ 4 × 10 ⁻¹⁰ W Hz ^−1/2 and NEP _{100 K} ∼ 10 ⁻¹¹ in the low-frequency part of the sub-THz spectral range.

A model of the turn-on spread has been developed for the axisymmetric configuration characteristic of the optical triggering of power SiC thyristors. Results for plane- and axisymmetric cases are compared. It is shown that the initial stage of the spread, during ∼ (2–3)τ, where τ is the current rise time constant for the thyristor turn-on, is characterized by a relatively low spread velocity, especially in the axisymmetric case. It is demonstrated that, even for a comparatively large thyristor structure, self-similarity conditions are not valid even for the plane case.

This study applies CF ₄ plasma pretreatment to a buffer oxide layer to improve the performance of low-temperature polysilicon thin-film transistors (LTPS TFTs). Results show that the fluorine atoms piled up at the interface between the bulk channel and buffer oxide layer and accumulated in the bulk channel. The reduction of the trap states density by fluorine passivation can improve the electrical characteristics of the LTPS TFTs. It is found that the threshold voltage reduced from 4.32 to 3.03 V and the field-effect mobility increased from 29.71 to 45.65 cm ² V ⁻¹ S ⁻¹. In addition, the on current degradation and threshold voltage shift after stressing were significantly improved about 31% and 70%, respectively. We believe that the proposed CF ₄ plasma pretreatment on the buffer oxide layer can passivate the trap states and avoid the plasma induced damage on the polysilicon channel surface, resulting in the improvement in perform...

A study of LDMOS–SCR devices for SOI BCD technology is presented. The LDMOS–SCR is fully compatible with BCD process and can replace the LDMOS as a high voltage output driver. By comparison of the LDMOS and another ‘pnpn’ type of LDMOS–SCR, the triggering mechanism and ESD behavior are well discussed with both device simulation and TLP measurement. It is verified that the ESD performance of the LDMOS–SCR is much improved compared with the LDMOS.

Tin monosulfide (SnS) films are fabricated by a multilayer-based solid-state reaction method on the glass substrate. By varying the layer thickness ratios of tin to sulfur, Sn-S alloying films with different chemical compositions are prepared. The analysis of the structure, chemical composition, optical and electrical properties is performed to evaluate the quality of the SnS films. The SnS film with approximate stoichiometric ratio can be obtained when the layer thickness ratio of tin to sulfur is controlled to 1. The SnS film is well crystallized with strong (0 4 0) orientation and has a band gap of 1.45 eV. The resistivity and activation energy are about 500 Ω ⋅ cm and 0.06 eV, respectively, at room temperature. The carrier concentration is determined to be 2.8 × 10 ¹⁶ cm ⁻³.

ZnO epilayers with a thickness of ∼360 nm were directly grown on r-sapphire planes at different temperatures (550, 500, 450 °C) with metal-organic chemical vapor deposition. Residual strains along the vertical direction and optical properties of the epilayers were investigated by using a variety of techniques including x-ray diffraction, low-temperature photoluminescence (PL), cathodoluminescence and Raman scattering. Compressive strains were revealed to exist in all the epilayers. Their strengths were found to reduce with increasing growth temperature. In addition, the optical properties of the epilayers were studied and the relationship between the strain and PL peak position was unveiled.

InAlGaN/GaN heterostructure field effect transistors (HFETs) with a nearly lattice-matched barrier layer (thickness t _bar = 8.3 nm) are investigated. The focus is set on resolving the systematic dependence of device characteristics on the gate length L _G . Therefore, five different gate length devices with L _G ranging from 75 nm to 2 µm have been realized. Peak values of 460 mS mm ⁻¹ and 100 GHz for transconductance g _m and unity current gain cut-off frequency f _T are obtained for the 75 nm device. DC characteristics as well as the cut-off frequency f _T show systematic scaling with the gate length L _G . Nevertheless, short-channel effects appear for the short gate length devices in both DC and RF operation, and a critical minimum aspect ratio L _G / t _bar of 27 is identified f...

The current transport mechanisms of Ag Schottky contacts to Zn-polar and O-polar bulk ZnO single crystals were investigated over the temperature range of 100–300 K. Using the thermionic emission (TE) model, Schottky contacts to Zn-polar face were found to have higher barrier heights (lower ideality factors) than those to O-polar face. Compared to the theoretical value of n-type ZnO, the higher Richardson constant was obtained for both polar faces in the modified Richardson plot, indicating that the TE model, which considers barrier inhomogeneity, cannot adequately explain the current transport. Temperature-dependent tunneling characteristics showed that the tunneling current was dominant for the Zn-polar face over the entire temperature range (100–300 K). For the O-polar face, the tunneling current was dominant mainly at low temperatures (100–200 K) and the TE component contributed strongly to the current transport above 200 K.