Low-voltage low-power CMOS RF low noise amplifier

In this paper, a 1 V, 2 GHz CMOS low-noise amplifier (LNA) was developed intended for use in the front-end receiver. The circuit is simulated in standard $0.25\mathrm{\mu }\mathrm{m}$ CMOS MOSIS. The LNA gain is 25.675 dB, noise figure (NF) is 4 dB, reverse isolation $(S_{12})$ is $-134.3\mathrm{dB}$, input return loss $(S_{11})$ is $-14.6\mathrm{dB}$, output return loss $(S_{22})$ is $-13.34\mathrm{dB}$, and the power consumption is 5.13 mA from a single 1 V power supply. One of the features of the proposed design is using a three-component cascode limitation, one of it is a transistor, to reduce the supply voltage.     

Low complexity PAPR reduction techniques for clipping and quantization noise mitigation in direct-detection O-OFDM systems

We present different distortionless peak-to-average power ratio (PAPR) reduction techniques that can be easily applied, without any symmetry restriction, in direct-detection (DD) optical orthogonal frequency division multiplexing (O-OFDM) systems based on the fast Hartley transform (FHT). The performance of DD O-OFDM systems is limited by the constraints on system components such as digital-to-analog converter (DAC), analog-to-digital converter (ADC), the Mach–Zehnder modulator (MZM) and electrical amplifiers. In this paper, in order to relax the constraints on these components, we propose to symmetrically clip the transmitted signal and apply low complexity (LC) distortionless PAPR reduction schemes able to mitigate, at the same time, PAPR, quantization and clipping noise. We demonstrate that, applying LC-selective mapping (SLM) without any additional transform block, the PAPR reduction is $1.5\text{dB}$ with only one additional FHT block using LC-partial transmit sequence (PTS) with random partitions; up to $3.1\text{dB}$ reduction is obtained. Moreover, the sensitivity performance and the power efficiency are enhanced. In fact, applying LC PAPR reduction techniques with one additional transform block and a 6 bit DAC resolution, the required receiver power for 8 dB clipping level and for a ${10}^{-3}\text{BER}$ is reduced by $5.1\text{dB}$.     

Study on the physical properties of europium doped indium oxide thin films

Structural, morphological, optical and electrical properties of europium doped In₂O₃ thin films grown by spray pyrolysis technique are studied in this work. The atomic percentages of europium dopant in In₂O₃-based solution were y = ${\left(\frac{{[\mathit{Eu}}^{3+}]}{{[\mathit{In}}^{3+}]}\right)}_{\mathit{sol}}$=0; 0.1; 0.3 and 0.5 at%. All films crystallize into the body centered cubic structure. The preferred orientation peak along the (222) plane was changed to (400) after doping. It is further revealed a best crystallinity for y =0.3 at% followed by a noticeable increase of the grain size. Some structural and microstructural parameters are determined using Rietveld refinement of XRD patterns. The optical transmission of doped films was above 68% in the visible range. The optical band gap (E_g) is in the range of [3.43–3.51] eV. Optical constant such as refractive index (n), packing density (p), porosity, oscillator energy (E₀) an_d dispersive energy (E_d) were also studied in this report using envelope method based on transmission-reflection spectra. Electrical properties show a lowest resistivity (ρ) for a doping concentration equals to 0.3 at% reaching 0.031 Ω cm. At this doping ratio, an enhancement of free carrier concentration is also remarked. A heat treatment under nitrogen atmosphere is then applied on optimized In₂O₃:Eu (0.3 at%). A significant decrease of the resistivity is noted at 250 °C during 2 h reaching 0.004 Ω cm. These results lead to conclude that annealed In₂O₃:Eu(0.3 at%) can be a good candidate to be used in many optoelectronic devices and especially as optical window or transparent electrode in solar cells.     

Theoretical and numerical investigations of carriers transport in N-semi-insulating-N and P-semi-insulating-P diodes – A new approach

A new and simple theoretical model is developed for ambipolar transport in compensated N-semi-insulating (SI)-N or P-SI-P diodes and is validated with exact J–V_a characteristics obtained through numerical modelisation. The electrical parameters used correspond to SI GaAs layers, but these results are valid for other compounds such as SI InP and InGaP. A relation between the bulk non-equilibrium excess carrier concentrations, valid for low and intermediate applied voltage, is first established. For a deep donor (N_t) compensating a residual shallow acceptor (N_A): $(n-n_{\text{e}})\approx \frac{{\tau }_{\text{nt}}}{{\tau }_{\text{pt}}}\left(\frac{N_{\text{t}}-N_{\text{A}}}{N_{\text{A}}}\right)(p-p_{\text{e}})$, where n_e and p_e are the thermal equilibrium free carrier densities in the SI layer, τ_nt, τ_pt and n_1t, p_1t are the familiar Shockley–Read–Hall (SRH) parameters of the deep trap. This relation represents an extension of the well known quasi space charge neutrality condition: (n ? n_e) ≈ (p ? p_e) valid for extrinsic semiconductors. We show then that a linear J–V_a relationship is observed in N-SI-N diodes when ${\mathbf{M}}_{\mathbf{t}}(=\frac{N_{\text{A}}}{(N_{\text{t}}-N_{\text{A}})}\frac{{\tau }_{\text{nt}}}{{\tau }_{\text{pt}}}\frac{p_{1\text{t}}}{n_{1\text{t}}})<1$ and in P-SI-P diodes when: M_t > 1. The quasi totality of the applied voltage V_a is lost across the SI layer and the electric field is constant (E ≈ V_a/L_SI). M_t < 1 characterizes a SI(N^?) layer where a strong hole depletion (p ≈ 0) across the SI bulk is associated to an “ohmic” electron current where n is constant but such that n < n_e. M_t > 1 characterizes a SI(P^?) layer where forn ≈ 0, p < p_e. On the other hand, the J–V_a characteristics of N-SI(P^?)-N diodes and P-SI(N^?)-P diodes show a saturation effect. Most of the applied voltage is now lost across the reverse biased contact and the electric field is low across the SI layer. For M_t values close to 1, we switch from a linear to a saturation regime. Equivalent relations are given for a deep acceptor compensating a shallow donor. We present results for short SI layers having lengths L_SI in the micrometer range and of the order or inferior to the ambipolar diffusion length L_Da, such layer are used as insulating layers in buried heterostructures for diode laser technology, as well as for long SI layers, L_SI ? L_Da, as used in radiation detectors technology.     

Epitaxial lateral overgrowth of InP/GaAs (1 0 0) heterostructures by metalorganic chemical vapor deposition

Epitaxial lateral overgrowth (ELOG) was used to grow InP on GaAs(1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). The selectivity of InP by ELOG is excellent and the regrowth InP epilayers have good morphology without polycrystalline on SiO₂ mask. The [$0\overline{1}1$] directional mask stripes and high V/III ratio are benefit to InP lateral growth. Compared to conventional direct growth, ELOG is effective in reducing the dislocation density, relaxing compressing strain in epilayers. In addition, the full width at half maximum (FWHM) of X-ray diffraction (XRD) ω scans and room temperature (RT) photoluminescence (PL) for a 3 μm thick epilayer by ELOG are 198 arcsec and 44 meV, respectively.