We discuss state of the art microLED performance for AR and direct view display applications, including a detailed comparison of both InGaN and AlInGaP material systems at various sizes from <2micron to >10micron pixels. In particular, we detail our most recent results on efficiency, gamut coverage, and reliability. We also quantify how sidewall passivation can lead to high IQE for 2 micron scale devices. Further we describe early results for a polychromatic LED demonstration that represents a possible breakthrough display technology.

We present state of the art for microLED materials, devices, and reliability. We show performance efficiencies as a function of current density and device size for InGaN Red, Green, and Blue and AlInGaP Red materials and breakdown EQE into constituent IQE and extraction efficiency. We also present reliability results for these structures across all materials systems. We then review several concurrently developed technologies that serve to maximize microLED performance in application use.

This paper presents state of the art for materials and devices for use in low‐power wearable displays. We present efficiencies for InGaN‐R, G, B, and AllnGaP‐R materials, as well as the dependence of performance on current density and emitter size. We further show how display efficiency can benefit from the presented level of microLED performance and contrast various material systems and optimal driving conditions for different display sizes and applications.

Applying the optimum rate of fertilizer nitrogen (N) is a critical factor for field management. Multispectral information collected by active canopy sensors can potentially indicate the leaf N status and aid in predicting grain yield. Crop Circle multispectral data were acquired with the purpose of measuring the reflectance data to calculate vegetation indices (VIs) at different growth stages. Applying the optimum rate of fertilizer N can have a considerable impact on grain yield and profitability. The objectives of this study were to evaluate the reliability of a handheld Crop Circle ACS-430, to estimate corn leaf N concentration and predict grain yield of corn using machine learning (ML) models. The analysis was conducted using four ML models to identify the best prediction model for measurements acquired with a Crop Circle ACS-430 field sensor at three growth stages. Four fertilizer N levels from deficient to excessive in 50/50 spilt were applied to corn at 1–2 leaves, with visible leaf collars (V1–V2 stage) and at the V6–V7 stage to establish widely varying N nutritional status. Crop Circle spectral observations were used to derive 25 VIs for different growth stages (V4, V6, and VT) of corn at the W. B. Andrews Agricultural Systems farm of Mississippi State University. Multispectral raw data, along with Vis, were used to quantify leaf N status and predict the yield of corn. In addition, the accuracy of wavelength-based and VI-based models were compared to examine the best model inputs. Due to limited observed data, the stratification approach was used to split data to train and test set to obtain balanced data for each stage. Repeated cross validation (RCV) was then used to train the models. Results showed that the Simplified Canopy Chlorophyll Content Index (SCCCI) and Red-edge ratio vegetation index (RERVI) were the most effective VIs for estimating leaf N% and that SCCCI, Red-edge chlorophyll index (CIRE), RERVI, Soil Adjusted Vegetation Index (SAVI), and Normalized Difference Vegetation Index (NDVI) were the most effective VIs for predicting corn grain yield. Additionally, among the four ML models utilized in this research, support vector regression (SVR) achieved the most accurate results for estimating leaf N concentration using either spectral bands or VIs as the model inputs.

Changes in spatial and temporal variability in yield estimation are detectable through plant biophysical characteristics observed at different phenological development stages of corn. A multispectral red-edge sensor mounted on an Unmanned Aerial Systems (UAS) can provide spatial and temporal information with high resolution. Spectral analysis of UAS acquired spatiotemporal images can be used to develop a statistical model to predict yield based on different phenological stages. Identifying critical vegetation indices (VIs) and significant spectral information could lead to increased yield prediction accuracy. The objective of this study was to develop a yield prediction model at specific phenological stages using spectral data obtained from a corn field. The available spectral bands (red, blue, green, near infrared (NIR), and red-edge) were used to analyze 26 different VIs. The spectral information was collected from a cornfield at Mississippi State University using a MicaSense multispectral red-edge sensor, mounted on a UAS. In this research, a new empirical method used to reduce the effects of bare soil pixels in acquired images was introduced. The experimental design was a randomized complete block that consisted of 16 blocks with 12 rows of corn planted in each block. Four treatments of nitrogen (N) including 0, 90, 180, and 270 kg/ha were applied randomly. Random forest was utilized as a feature selection method to choose the best combination of variables for different stages. Multiple linear regression and gradient boosting decision trees were used to develop yield prediction models for each specific phenological stage by utilizing the most effective variables at each stage. At the V3 (3 leaves with visible leaf collar) and V4-5 (4-5 leaves with visible leaf collar) stages, the Optimized Soil Adjusted Vegetation Index (OSAVI) and Simplified Canopy Chlorophyll Content Index (SCCCI) were the single dominant variables in the yield predicting models, respectively. A combination of the Green Atmospherically Resistant Index (GARI), Normalized Difference Red-Edge (NDRE), and green Normalized Difference Vegetation Index (GNDVI) at V6-7, SCCCI, and Soil-Adjusted Vegetation Index (SAVI) at V10,11, and SCCCI, Green Leaf Index (GLI), and Visible Atmospherically Resistant Index (VARIgreen) at tasseling stage (VT) were the best indices for predicting grain yield of corn. The prediction models at V10 and VT had the greatest accuracy with a coefficient of determination of 0.90 and 0.93, respectively. Moreover, the SCCCI as a combined index seemed to be the most proper index for predicting yield at most of the phenological stages. As corn development progressed, the models predicted final grain yield more accurately.

Induction motors are one of the most widely used machines that are used in industrial motion control and home systems. On the other hand, the optimal determination parameters have a direct and significant effect on their efficiency, longevity, and performance. Determining the initial parameters of these machines by the classic method is time-effective and costly. Therefore in recent years, the use of computer processing such as simulation, heuristical algorithm, ANN, etc. has become common as an alternative method in this field. Cuckoo Optimization Algorithm (COA) is a relatively new algorithm and it is less used to solve this nonlinear problem. In this article, the parameter of the induction machine will be estimated using COA. COA. In the following, the results obtained from the algorithm will be compared with the results obtained from several examples of conventional algorithms. Objective functions are defined as minimizing the true values of the relative error between the measured and estimated torques of the machine in different slips. Objective functions have been used to optimize the parameters of the induction motor with an approximate equivalent circuit and the induction motor with the exact circuit. The final results show the accuracy of operation and very good convergence speed of the algorithm in solving the problem.

We report on a comparison study of the electrical and optical properties of a set of device structures with different numbers of cascade stages, type-II superlattice (T2SL) absorber thickness, and doping variations, as well as a noncurrent-matched interband cascade infrared photodetectors (ICIP) structure with equal absorbers. Multistage ICIPs were demonstrated to be capable of operating at high temperatures at zero-bias with superior carrier transport over comparable conventional one-stage detectors. Based on the temperature dependence and bias sensitivity of their responsivities with various absorber thicknesses, the diffusion length is estimated to be between 0.6 and 1.0 mu m for T2SL materials at high temperatures (>250 K). A comparison of responsivities between current matched ICIPs with varied absorber thicknesses and noncurrent-matched ICIPs with equal absorbers shows that the current-matching among cascade stages is necessary to maximize responsivity. Additionally, electrical gain exceeding unity is demonstrated in these detectors in the reverse-illumination configuration. (c) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

We report on an investigation of multiple negative differential conductance (NDC) features in long wavelength interband cascade infrared photodetectors (ICIPs) at and above 300 K. Using ICIPs with various structures and carrier concentrations, we employ several approaches to demonstrate that the observed multiple NDC features and their unusual temperature dependence are related to the sequential turn off of resonant tunneling of minority carriers through the electron barriers at high temperatures.

Downward shortwave radiation is a key quantity in the land-atmosphere interaction. Since the moderate resolution imaging spectroradiometer data has a coarse temporal resolution, which is not suitable for estimating daily average radiation, many efforts have been undertaken to estimate instantaneous solar radiation using moderate resolution imaging spectroradiometer data. In this study, the principal components analysis technique was applied to capture the information of moderate resolution imaging spectroradiometer bands, extraterrestrial radiation, aerosol optical depth, and atmospheric water vapour. A regression model based on the principal components was used to estimate daily average shortwave radiation for ten synoptic stations in the Fars province, Iran, for the period 2009-2012. The Durbin-Watson statistic and autocorrelation function of the residuals of the fitted principal components regression model indicated that the residuals were serially independent. The results indicated that the fitted principal components regression models accounted for about 86-96% of total variance of the observed shortwave radiation values and the root mean square error was about 0.9-2.04 MJ m(-2) d(-1). Also, the results indicated that the model accuracy decreased as the aerosol optical depth increased and extraterrestrial radiation was the most important predictor variable among all.

We report on the characterization of narrow-bandgap (E-g approximate to 0.4 eV, at 300 K) interband cascade thermophotovoltaic (TPV) devices with InAs/GaSb/AlSb type-II superlattice absorbers. Two device structures with different numbers of stages (two and three) were designed and grown to study the influence of the number of stages and absorber thicknesses on the device performance at high temperatures (300-340 K). Maximum power efficiencies of 9.6% and 6.5% with open-circuit voltages of 800 and 530 mV were achieved in the three-and two-stage devices at 300 K, respectively. These results validate the benefits of a multiple-stage architecture with thin individual absorbers for efficient conversion of infrared radiation into electricity from low-temperature heat sources. Additionally, we developed an effective characterization method, based on an adapted version of Suns-V-oc technique, to extract the device series and shunt resistance in these TPV cells.

The family of interband cascade (IC) IR devices includes: interband cascade lasers (ICLs), interband cascade IR photodetectors (ICIPs), and thermophotovoltaics (ICTPVs). To date, developments at the component level have resulted in power-efficient mid-IR ICLs with CW operation at room temperature and above as well as uncooled mid-IR low-noise and high-speed ICIPs. However, there has been little effort to integrate these devices on a single chip for an IR photonic system. Since an appropriately designed ICL can operate as an IR photodetector at zero bias, ICLs and ICIPs can be grown and fabricated on a single chip, enabling the on-chip integration of IR lasers and photodetectors for mid- and long-IR wavelengths. We report the first demonstration of monolithically integrated mid-IR IC devices operating at room temperature. The unit consists of a monolithically integrated ICL and ICIP fabricated using focused ion beam (FIB) milling. The base structure is a type-I ICL with quaternary GaInAsSb active regions. The laser peak emission wavelength is 3.1 μm at 20 ◦C and the 10% cut-off wavelength of the corresponding ICIP is 3.3 μm, which ensures sufficient photon absorption at the lasing wavelength. For a laser/detector unit (at 20 ◦C) with a 12 μm gap between laser mirror and detector, the open-circuit voltage of the ICIP is 1.06 V and its short-circuit current is 106 μA, resulting from the laser emission (2.6 mW/facet). These preliminary results demonstrate the practical application of integrated IC devices for high-temperature, high-bandwidth and power-efficient on-chip sensors and optical communication mid-IR photonic systems.

High temperature operation of long wavelength interband cascade infrared photodetectors (ICIPs) has been demonstrated with a working temperature above 300 K. We conducted a comparison study of three sets of ICIP structures, which comprise single absorber barrier detectors and multi-stage ICIPs with four, six and eight discrete absorbers. The 90% cutoff wavelength of these detectors was between 7.5 and 11.5 μm from 78 to 340 K. Advantages of the multi-stage ICIPs over the one-stage devices are demonstrated in terms of lower dark current density, higher detectivity (D*) and higher operating temperatures. Multiple stage ICIPs were able to operate at temperatures up to 340 K with a monotonically increasing bias-independent responsivity up to 280 K, while the one-stage detectors operated at temperatures up to 250 K with the responsivity decreased at 200 K with bias dependence. The D* values for these ICIPs at 200 and 300 K were higher than 1.0×109 and 1.0×108 cmˑHz1/2/W at 8 μm, respectively, which is more than a factor of two higher than the corresponding values for photovoltaic HgCdTe detectors with similar cutoff wavelengths. Interestingly, negative differential conductance (NDC) was observed in these detectors at high temperatures. The underlying physics of the NDC was investigated and correlated with the number of cascade stages and electron barriers. With enhanced electron barriers in the multiple-stage ICIPs, the NDC was reduced, and the device performance, in terms of D*, was improved.

Interband cascade (IC) devices are a family of quantum engineered heterostructures that include: IC lasers (ICLs), IC infrared photodetectors (ICIPs) and IC thermophotovoltaic (ICTPV) devices. In these structures, the transport of carriers across different stages is made possible by the type-II broken-gap band alignment between InAs and GaSb. Many shortcomings in conventional single absorber narrow-bandgap devices, such as short carrier lifetime and limited diffusion length (particularly at high temperatures) can be addressed by a multiple-stage architecture. While multiple photons need to be absorbed to output one electron in a multi-stage detector or photovoltaic cell, the multiple-stage architecture has some big benefits, especially at high temperatures and long wavelengths. The multiple excitations (depending on the number of stages) of each electron in an ICIP result in lower noise (higher signal-to-noise) than conventional single-stage detectors with thick absorbers. Furthermore, by keeping individual absorbers shorter than the minority carrier diffusion length most of the photogenerated carriers can be collected. This efficient collection of photogenerated carriers along with the high open-circuit voltages lead to high conversion efficiencies in ICTPV devices. The theoretical and experimental exploration of these properties of ICIPs and ICTPV devices are the main focus of this dissertation. Design and characterization of ICIPs in different bands including short- through very long-wavelength IR are discussed in detail. It is shown that a multiple-stage detector has superior performance over a single-stage detector at high temperatures. In contrast to single-stage detectors, in ICIPs high-frequency bandwidths can be achieved with no compromise on the device sensitivity. The high-frequency modeling and characterization of ICIPs reveal gigahertz bandwidth (~1.3 GHz) with high detectivity (˃1E9 cm.Hz1/2/W) for three-stage mid-IR ICIPs at 300 K. A comparative study of time domain characteristics (i.e., eye diagrams) of single-stage detectors and ICIPs (with the total absorber thickness equal to that of the single-stage devices) confirmed the higher bandwidth and shorter fall and rise times in ICIPs. The unidirectional flow of carriers in IC lasers makes their structure feasible for infrared detection. Therefore, it is possible to realize monolithically integrated lasers and detectors on a single chip. Since the detector section is edge-illuminated in these bi-functional devices, detectivities higher than 1E10 cm.Hz1/2/W were estimated for these detectors at room temperature (RT). High-detectivity and high-speed ICIPs along with low power consumption ICLs make monolithically integrated IC lasers and detectors a practical choice for compact spectrometers and lab-on-a-chip devices. Two sets of ICTPV devices (Eg < 0.5 eV) were investigated to understand the influence of number of stages/absorber thickness on the TPV cells performance. Efficiencies up to ~10% were achieved in three-stage ICTPVs with 0.41 eV bandgap.…

We report on the room-temperature operation of a high-speed mid-infrared optical system (f3-dB ≈ 0.5 GHz). This system consists of an efficient interband cascade laser and an uncooled high-performance interband cascade infrared photodetector.

The high-frequency operation of a mid-infrared interband cascade system that consists of a type-I interband cascade laser and an uncooled interband cascade infrared photodetector (ICIP) is demonstrated at room temperature. The 3-dB bandwidth of this system under direct frequency modulation was ∼850 MHz. A circuit model was developed to analyze the high-frequency characteristics. The extracted 3-dB bandwidth for an uncooled ICIP was ∼1.3 GHz, signifying the great potential of interband cascade structures for high-speed applications. The normalized Johnson-noise-limited detectivity of these ICIPs exceeded 109 cm Hz1/2/W at 300 K. These results validate the advantage of ICIPs to achieve both high speed and high sensitivity at high temperatures.

We report on the demonstration of a monolithically integrated mid-IR interband cascade (IC) laser and photodetector operating at room temperature. The base structure for the integrated laser and detector is a six-stage type-I IC laser with GaInAsSb quantum well active regions. The laser/detector pair was defined using focused ion beam milling. The laser section lased in cw mode with an emission wavelength of ∼3.1 μm at 20 °C and top-illuminated photodetectors fabricated from the same wafer had Johnson-noise-limited detectivity of 1.05 × 109 cm Hz1/2/W at this wavelength and temperature. Under the same condition, the detectivity for the edge illumination configuration for the monolithically integrated laser/photodetector pairs is projected to be as high as 1.85 × 1010 cm Hz1/2/W, as supported by experimentally observed high photocurrent and open-circuit voltage. These high performance characteristics for monolithically integrated IC devices show great prospects for on-chip integration of mid-IR photonic devices for miniaturized sensors and on-chip optical communication systems.

In this paper, the price of electric energy in the electricity market is predicted using neural networks. Multi-Layer Perceptron neural network is proposed for electricity market price prediction and Back propagation algorithm is used for neural network training. Since the load changes taking one of the factors affecting the price of electrical energy, Electric load as an important factor in predicting market price is considered in this article. Two models have been used for electricity market price prediction, and results of two methodes have been compared. Data used in this paper is related to Nord Pool Spot Market in 2015, Nord Pool Spot runs the largest market for electrical energy in Europe

In this work, we report the demonstration of quaternary GaInAsSb-based mid-wavelength infrared photodetectors with cutoff wavelengths longer than 4 mu m at 300 K. Both interband cascade infrared photodetector (ICIP) with a three-stage discrete absorber architecture and conventional one-stage detector structures have been grown by molecular beam epitaxy and investigated in experiments for their electrical and optical properties. High absorption coefficient and gain were observed in both detector structures. The three-stage ICIPs had superior carrier transport over the one-stage detectors. A detectivity as high as 1.0 x 10(9) cm Hz(1/2) W-1 was achieved at 3.3 mu m for both one- and three-stage detectors under zero bias at 300 K. The implications of these results are discussed along with potential of GaInAsSb-based ICIPs for high-speed applications.

We investigate high-temperature and high-frequency operation of interband cascade infrared photodetectors (ICIPs)-two critical properties. Short-wavelength ICIPs with a cutoff wavelength of 2.9 mu m had Johnson-noise limited detectivity of 5.8x10(9) cmHz(1/2)/W at 300 K, comparable to the commercial Hg1-xCdxTe photodetectors of similar wavelengths. A simple but effective method to estimate the minority carrier diffusion length in short-wavelength ICIPs is introduced. Using this approach, the diffusion length was estimated to be significantly shorter than 1 mu m at high temperatures, indicating the importance of a multiple-stage photodetector (e.g., ICIPs) at high temperatures. Recent investigations on the high-frequency operation of mid-wavelength ICIPs (lambda(o)= 4.3 mu m) are discussed. These photodetectors had 3-dB bandwidths up to 1.3 GHz with detectivities exceeding 1x10(9) cmHz(1/2)/W at room temperature. These results validate the ability of ICIPs to achieve high bandwidths with large sensitivity and demonstrate the great potential for applications such as: heterodyne detection, and free-space optical communication.