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Trapping of hot electron behavior by trap centers located in the buffer layer of a wurtzite phase GaN MESFET has been simulated using an ensemble Monte Carlo simulation. The simulated results show that trap centers are responsible for current collapse in GaN MESFET at low temperatures. These electrical traps degrade the performance of the device at low temperatures. On the other hand, at high temperatures, the electrical performances are improved due to electron emission from the trap centers. The simulated device geometries and doping are matched to the nominal parameters described for the experimental structures as closely as possible, and the predicted drain current and other electrical characteristics for the simulated device including the trapping center effects show much closer agreement with the available experimental data than without trap center effects.

Al₂O₃-doped zinc oxide (in AZO, the Al₂O₃ contents are approximately 2 wt.%) films have been grown by radio frequency (RF) magnetron sputtering at room temperature under varied sputtering pressures ranging from 3.5–15 mTorr. The electrical resistivity of AZO films is about 2.22×10^-3 Ωcm (sheet resistance ~ 89 Ω/square for a thickness ~ 250 nm), and the visible range transmittance is about 80% at the argon sputtering pressure of 15 mTorr and a RF power of 100 W. This study analyzes the structural, morphological, electrical and optical properties of AZO thin films grown on soda-lime glass substrate with 2, 5, and 10 nm thick Al buffer layers (and SiO₂ buffer). For the films deposited on the 2 nm thick Al buffer layer, we obtained a c-axis-oriented AZO/Al thin film on glass with the XRD full-width at half maximum (FWHM) of 0.31 and root mean square (RMS) surface roughness of about 3.22 nm. The lowest resistivity of 9.46×10^-4 Ωcm (sheet resistance ~ 37.87 Ω/square for a thickness ~ 250 nm) and a high transmittance (80%) were obtained by applying a 2 nm thick Al buffer layer. In contrast, the resistivity was slightly increased by applying the SiO₂ buffer layer.

Recent advances in silicon technology have pushed the silicon properties to its theoretical limits. Therefore, wide band gap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN) have been considered as a replacement for silicon. The discovery of these wide band gap semiconductors have given the new generation power devices a magnificent prospect of surviving under high temperature and hostile environments. The primary focuses of this review are the properties of GaN, the alternative substrates that can be used to deposit GaN and the substitution of SiO₂ gate dielectric with high dielectric constant (k) film. The future perspectives of AlGaN/GaN heterostructures are also discussed, providing that these structures are able to further enhance the performance of high power devices.

This work presents the results of synthesis and characterization of polycrystalline $n$-type Bi₂S₃ thin films. The films were grown through a chemical reaction from co-evaporation of their precursor elements in a soda-lime glass substrate. The effect of the experimental conditions on the optical, morphological structural properties, the growth rate, and the electrical conductivity $(\sigma )$ was studied through spectral transmittance, X-ray diffraction (XRD), atomic force microscopy (AFM) and $\sigma$ versus $T$ measurements, respectively. The results showed that the films grow only in the orthorhombic Bi₂S₃ bismuthinite phase. It was also found that the Bi₂S₃ films present an energy band gap $(E_g)$ of about 1.38 eV. In addition to these results, the electrical conductivity of the Bi₂S₃ films was affected by both the transport of free carriers in extended states of the conduction band and for variable range hopping transport mechanisms, each one predominating in a different temperature range.

Epitaxial CeO₂ seed layer and La₂Zr₂O₇ (LZO) buffer layers were deposited on biaxially-textured Ni–5 at.% W (NiW) tape substrate by liquid-phase polymer assisted nanoparticles deposition (PAND) method. LZO layers deposited by PAND have consistently shown tilting of the $c$-axis toward the direction of the sample’s surface normal. A new approach increasing the sharpening of the buffer texture by magnetic structural processing (MSP) of buffer layers was tested. The LZO layers, deposited on the seed and buffer layers after MSP, have dense and smooth surface structure, and more importantly, significantly improved out-of-plane texture, compared with the LZO layers that were deposited on a layer without MSP. Transmission electron microscopy study confirmed the $c$-axis tilting of CeO₂ and LZO layers and revealed the absence of interfaces between LZO layers which have been grown on the layers after MSP. There are very small (2–4 nm) gated pores in the single-crystal structure of LZO layers that are not typical for structure of LZO layers obtained by liquid-phase methods. Thus the LZO buffer layers can serve as an effective metal-ion diffusion barrier.

Cu₂ZnSnS₄ (CZTS) materials have been widely investigated due to their excellent properties in solar cell applications. The common reference structure for CZTS cells is Al:ZnO(AZO)/i-ZnO/CdS/CZTS, but it is critical to find a suitable buffer layer material to replace toxic cadmium (Cd). In addition, the efficiency of CZTS cells is improved by improving the doping type (n or p) and doping concentration of MoS₂ generated during the manufacturing process. wxAMPS was used to simulate the performance of a CZTS battery with an Al:ZnO/i-ZnO/Zn(O,S)/CZTS/(MoS₂) structure. The performance of batteries using Zn(O,S) and CdS as buffer layers was compared. The optimal thickness of CZTS layer and the doping concentration of CZTS layer were calculated, and the doping type and concentration of MoS₂ layer were analyzed and the performance of the battery was improved by optimizing the solar cell parameters. This work provides novel ideas for designing and manufacturing higher performance solar cells.