F. M. Guo

Weak light characteristics of a new photoelectric sensor with potential biosensor application

We have designed and developed a field deployable biosensor unit based on a novel proprietary quantum dots-quantum well hybrid structure. We analyzed in detail the detection sensitivity and in particular weak light detection and analysis of the semiconductor optoelectronic device. We designed a readout circuit and a data processing unit to handle the response signal. The sensor unit is equipped with a LCD element for data display and can be used in a centrally managed real-time monitoring system such as for infectious disease management and bio-aerosol monitoring. The high sensitivity of our sensor enables fast and reliable spectral results to aid rapid identification of biological samples.

Nano-Device Modeling for Charge-Sensitive Infrared Photodetector Used in Very Long Wavelength and THz

This paper discusses modeling for the design of charge-sensitive nano-device for 15μm wavelength using Crosslight Apsys software. First, a double quantum well heterostructure was established using Graphic User Interface. Second, a computer simulation program based on physical mechanisms involved such as intersubband optical transition was compiled and executed. The scan conditions and iterative algorithm were also carefully set up. Finally, band diagrams and I-V characteristics were obtained and were in good agreements with the measured result.

Red Blood Cell Count Automation Using Microscopic Hyperspectral Imaging Technology

Red blood cell counts have been proven to be one of the most frequently performed blood tests and are valuable for early diagnosis of some diseases. This paper describes an automated red blood cell counting method based on microscopic hyperspectral imaging technology. Unlike the light microscopy-based red blood count methods, a combined spatial and spectral algorithm is proposed to identify red blood cells by integrating active contour models and automated two-dimensional k-means with spectral angle mapper algorithm. Experimental results show that the proposed algorithm has better performance than spatial based algorithm because the new algorithm can jointly use the spatial and spectral information of blood cells.

Optimization and Analysis on Several Impact Factors of High-Gain Separate Absorption, Grading, Charge and Multiplication Avalanche Photodiodes

The band structure, current response, bias voltage distribution and the bias-gain relationship of InGaAsP-InP avalanche photodiode (APD) which comprise separate layer of absorption, grading, charge and multiplication (SAGCM) have been simulated in detail by software of APSYS. The current response discussed in the paper shows a significant improvement compared with the previous APD which used the SACM structure. Meanwhile an optimized SAGCM-APD structure is proposed to further reduce the punch-through voltage while electric field distribution keeps invariant, and its multiplication gain value dramatically increased, which is almost 5 times larger than that of former one.

Based simulation of high gain and low breakdown voltage InGaAs/InP avalanche photodiode

The InGaAs/InP avalanche photodiode (APD) of thin heterostructure charge layer has studied. Apsys software is used for simulation. For reducing the dark current and achieving higher avalanche gain, a 30 nm InP charge layer and 100 nm InGaAsP grade charge layer used between 400 nm multiplication and absorption layers. Simulation results demonstrated that the low dark current properties and low breakdown voltage (17.5 V) had achieved. The avalanche gain is 88 at reverse bias voltage 17.2 V, and reached 300 at 17.4 V before break down.

The study of MEMS millimeter wave phase shifter

Several designs of MEMS millimeter-wave phase shifters are presented. They consist of a coplanar waveguide (CPW) transmission line periodically loaded with 8/spl sim/32 metal bridges, functioning as capacitive switches. Every switching element consists of a thin metallic membrane actuated by applied bias. Remarkable phase shifter performances were observed. One MEMS phase shifter reached to 372/spl deg//3.5 mm under 20 V bias at 35 GHz, with an insertion loss (S/sub 21/) of about 4/spl sim/7 dB.

The novel assembly method of a field deployable biosensor unit

In this paper we report the novel assembly method of a biosensor unit based on 64 pixel photodetector array with a proprietary semiconductor quantum dots (QDs) quantum well (QW) hybrid structure. There is significantly lower dark current for optimized high sensitivity detector. The capacitive trans-impedance amplifier (CTIA)-correlated double sampling (CDS) readout circuit can readout weak optical signal which respond by photodetector. To minimize the packaging size of our biosensor unit, a double-sided printed circuit board designed to decrease noise by special package making photodetector array can operate at room temperature and lower temperature for get better performance. The readout circuit is bonding on the backside of substrate through silicon via (TSV) structure, and the photodetector array bonding on the front side of substrate for making the optic signal through to photosensitive window of detector. A highly integrated Cortex-M4 MCU (STM32F407) has build the data acquisition and analysis unit providing Wi-Fi interface to communicate with the PC software for biosensor unit rapid diagnosis infectious disease and more easy carry.

The experimental model of micro-cantilever switch and its optimization model

This paper studied the original model of the switch, which has a full-contact pull down voltage of 13.7V. And the RF results are measured firstly by Cascade 12000 microwave probe in order to calculate the parameter of the equivalent circuit. The equivalent circuit is built to study the RF performance and the s-parameters are studied by ADS. However, the high actuation voltage will degrade the switch life. Then four optimized geometric models are compared in order to obtain the lowest actuation voltage. Finally, the model of trapezium shape has the longest life span 1.452×106 and smallest full-contact down voltage 6.3V.

Dumping design of CTIA readout circuit based on a low-dimensional quantum structure photoelectric sensor

A practical equivalent circuit model of the low dimensional photoelectric sensor with quantum dots-quantum well (QDs-QW) hybrid hetero-structure is introduced in this article. This model acts as a signal source for ROIC (readout integrate circuit) simulation. An optimal readout integrated circuit employing capacitor feedback transimpedance amplifier (CTIA) structure is designed for the QDs-QW hybrid hetero-structure photoelectric sensor. Based on the photoelectron storage characteristic of the photoelectric sensor, a dumping structure for CTIA readout integrated circuit is studied. This dumping structure is proposed to release the redundant charge stored by the device for improving the performance of the photoelectric sensor readout.

MEMS Phase Shifters On Low-resistivity Silicon Wafer

The basic structure of MEMS millimeter-wave phase shifters was consisted of a coplanar waveguide (CPW) transmission line periodically loaded with several thin metallic membranes. A new method was developed to obtain lower-loss microwave coplanar waveguide (CPW) by means of forming porous silicon (PS) on low-resistivity silicon wafer. The CPW fabricated on porous silicon (PS)/oxidated porous silicon (OPS) coated with polyimide had demonstrated lower loss than 0-7.5 dB/1.2 cm in 0-40 GHz, and comparison with quartz, low-resistivity silicon and multi-structure of poly-Si/SiO2 on high-resistivity silicon in measure and analysis