A quantitative analysis of electronic transport in n- and p-type modulation-doped GaAsBi/AlGaAs quantum well structures

Electronic transport properties of as-grown and thermally annealed n- and p-type modulation-doped GaAsBi/AlGaAs quantum well (QW) structures were investigated. Hall mobility of as-grown, n- and p-type modulation doped QW structures are found from raw experimental data as ∼1414 and 95 cm2 Vs−1 at room temperature. A comparison between reported two-dimensional (2D) electron density determined from the analyses of Shubnikov de Haas oscillations and the 2D Hall electron density indicates a presence of parallel conduction in barrier layer (AlGaAs) and QW layer (GaAsBi) in n-type samples, therefore a parallel channel conduction theory is used to separate the electron mobility in the QW and the barrier layers in n-type modulation doped GaAsBi/AlGaAs QW structure. The extracted electron mobility of the as-grown n-type GaAsBi/AlGaAs QW sample is determined as ∼5975 cm2 Vs−1 at 4.2 K, which is closer to the electron mobility in GaAs. It is found that thermal annealing at lower temperature than growth temperature increases electron mobility of 2D electron gas, while annealing at higher temperature than growth temperature decreases electron mobility. The temperature dependence of the extracted electron mobility using parallel conduction approximation is analytically calculated by considering possible scattering mechanisms. Analysis of temperature-dependent electron mobility shows that the dominant scattering mechanisms are interface roughness (IFR), acoustic, and alloy-potential scatterings at low and intermediate temperature range, and IFR and optical phonon scattering at the high-temperature range in n-type modulation doped GaAsBi/AlGaAs QW structures.acceptedVersionPeer reviewe

In-depth analysis on PTB7 based semi-transparent solar cell employing MoO3/Ag/WO3 contact for advanced optical performance and light utilization

Abstract Novel semi-transparent organic solar cells (ST-OSC) can be designed with high average visible transmittance (AVT) while at the same time exhibiting superior photovoltaic performance. This reach requires their design to be based not only on conventional window applications but also on functional industrial applications that require exceptional optical performance. In ST-OSC, high AVT can be achieved by photonic-based dielectric/metal/dielectric (DMD) transparent contact engineering. Functional optical modification can also be made with a fine-tuned design of DMD that includes a light management engineering-based approach. Thus, ST-OSCs can be suitable for aesthetic, colourful and decorative industrial windows that provide natural lighting. In this study, we determined optimal ST-OSCs based on a novel PTB7:PC71BM polymer blend with MoO3/Ag/WO3 asymmetric DMD top contact by examining extraordinary optical properties such as AVT, colour rendering index, correlated colour temperature and colour perception over 10 thousand designs. In addition to determining the optimality and extraordinary optical limits for PTB7, we also evaluated the photon-harvesting and photovoltaic performance of ST-OSCs from external quantum efficiency and quantum utilization efficiency. In optimal situations, ST-OSCs offering 48.75% AVT, 99.08 CRI, and sky-blue colours were designed and determined to generate short-circuit current densities of 9.88 mA·cm−2, 13.64 mA·cm−2, and 13.06 mA·cm−2, respectively

Functional optical design of thickness-optimized transparent conductive dielectric-metal-dielectric plasmonic structure

Dielectric/metal/dielectric plasmonic transparent structures play an important role in tailoring the high-optical performance of various optoelectronic devices. Though these structures are in significant demand in applications, including modification of the optical properties, average visible transmittance (AVT) and colour render index (CRI) and correlated colour temperature (CCT), obtaining optimal ones require precise thickness optimization. The overall objective of this study is the estimation of the optimal design concept of MoO3/Ag/WO3 (10/d(Ag)/d(WO3) nm) plasmonic structure. To explore the proper use in optoelectronic devices, we are motivated to conduct a rigorous optical evaluation on the thickness of layers. Having calculated optical characteristics and achieved the highest AVT of 97.3% for d(Ag) = 4 nm and d(WO3) = 6 nm by the transfer matrix method, it is quite possible to offer the potential of the structure acting as a transparent contact. Notably, the colour coordinates of the structure are x = 0.3110 and y = 0.3271, namely, it attributes very close to the Planckian locus. This superior colour performance displays that MoO3/Ag/WO3 shall undergo rapid development in neutral-colour windows and LED technologies. Structure with d(Ag) = 6 nm and d(WO3) = 16 nm exhibits the highest CRI of 98.58, thus identifying an optimal structure that can be integrated into LED lighting applications and imaging technologies. Besides the colour of structure with d(Ag) = 4 nm and d(WO3) = 8 nm is equal for D65 Standard Illuminant, the study reports that the range of CCTs are between 5000 and 6500 K. This optimization makes the structure employable as a near-daylight broadband illuminant. The study emphasizes that optimal MoO3/Ag/WO3 plasmonic structures can be used effectively to boost optoelectronic devices' performance

Investigation of V-groove fabricated GaInNAs nipi solar cell structure

© 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.An anisotropic etching of 1 eV Ga0.92In0.08N0.03As0.97 grown on (100) p-type GaAs substrate was investigated. Effects of the V-groove etching profile and metallization on the photovoltaic performance of the GaInNAs nipi solar cell with five periods are presented. Experimental results were supported by simulation studies considering the metal–semiconductor junction characteristics in the electrodes of nipi photovoltaic device. Standard wet etching processes at room temperature is applied using sulfuric acid based H2SO4: H2O2: H2O [1:8:8] solution to form the V-groove shape on the nipi sample. The etching characteristics in the [100] and 〈 011 〉 crystal directions are determined by using an interdigitated square spiral photolithographic mask. The scanning electron microscope (SEM) is used to analyze the V-groove etch profile. Two type of V-grooves achieved, one of them is in the [1 1 ¯ 1] direction and suitable to form metal electrodes for nipi layers and the second one is in [1 ¯ 11] direction can be called a dovetail groove and not suitable for metal coating. Experimentally, the improvements observed in the short circuit current, open circuit voltage, and efficiency of the device despite some metallization failures. The effect of the metallization quality on the response to the spectrum can be clearly seen from the photovoltage spectrum. Essentially, these experimental results show that GaInNAs nipi devices have the potential to become high efficiency solar cells. Moreover, it can be possible to achieve high performance by integrating nipi devices into multijunction solar cells

Determination of surface morphology and electrical properties of MoO3 layer deposited on GaAs substrate with RF magnetron sputtering

We report the effects of the substrate temperature on the surface morphology of Molybdenum tri-oxide (MoO3) thin films and the electrically detailed examination of Au/MoO3/n-GaAs MOS heterojunction structure with the best homogeneity. MoO3 thin film was deposited both on soda-lime silicate glass as a thin film and n-type and (100) oriented GaAs substrates using RF magnetron sputtering method at substrate temperatures of room temperature, 100 degrees C, 200 degrees C and 300 degrees C. Surface morphology of the MoO3 thin films were investigated by utilizing atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. AFM and SEM results have shown that MoO3 thin film with substrate temperature of 200 degrees C has the lowest surface roughness and the homogeneity of the film structures significantly enhances with increasing substrate temperature up to 200 degrees C. An inclement in roughness of thin film structure was detected at higher temperature than 200 degrees C due to the deterioration of homogeneity. Therefore, we primarily focused on the MoO3 thin films produced at the substrate temperature of 200 degrees C to examine the electrical properties of Au/MoO3/n-GaAs MOS heterojunction device. In order to determine the electrical properties, temperature dependent I - V measurements were performed in between 200 and 400 K by steps of 25 K. The fundamental electrical parameters such as saturation current (I-0), ideality factor (n), and barrier height (phi(0)) were calculated by analyzing the forward bias I-V curves at different temperatures. The series resistance (R-s) values of the device were also determined using the plot of structure resistance (R-i) vs applied bias voltage (V-i), Thermionic Emission Theory and Cheung and Cheung methods. The R-s value of Au/MoO3/n-GaAs MOS heterojunction device shows an abnormal behavior of up to 350 K, which is the critical temperature value and tends to increase with increasing temperature. Above the critical temperature value, it exhibits ideal behavior