Comparison of neutron irradiation effects on the electrical performances of SiGe HBT and SiBJT

The change of electrical performances of silicon-germanium (SiGe)heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) was studied as afunction of reactor fast neutron radiation fluence. Alter neutron irradiation, the collector currentI_c and the current gain beta decrease, and the base current I_b increases generally for SiGe HBT.The higher the neutron irradiation fluence is, the larger I_b increases. For conventional Si BJT,I_c and I_b increase as well as beta decreases much larger than SiGe HBT at the same fluence. It isshown that SiGe HBT has a larger anti-radiation threshold and better anti-radiation performance thanSi BJT. The mechanism of performance changes induced by irradiation was preliminarily discussed.

Analysis of the abnormal resistance in AlGaN/GaN heterostructure's ohmic contact tests

Ti/Al/Ti/Au and Ti/Al/Ni/Au ohmic contacts were fabricated on AlGaN/GaN heterostructure under different temperatures of rapid thermal processing （RTP）. Since abnormal resistance values were observed during the contact resistance testing,the surface morphology and contact borders of the samples were analyzed to determine the physical mechanism. Such abnormal phenomenon is found to originate from cracking of the AlGaN layer during RTP,flowing of Ti/Al metallic liquid along the crevices,and continuous reaction of the metallic liquid with AlGaN/GaN. Such processes result in abnormal conduction channels. The possible mechanism of the crevice formation was discussed,and the possible solutions to avoid the crevices were proposed.

Electron irradiation effects on DC electrical performances of SiGe HBT in a comparison with Si BJT

The DC characteristics of SiGe HBT irradiated at different electron dose havebeen studied in a comparison with those of Si B JT. Generally, I_b and I_b - I_(b0) increase, I_c,I_c -I_(c0) and its +/- transition V_(be) as well as DC current gain ft decreases with increasingdose; increase of I_b -I_(b0) with increasing dose for Si BIT is much larger than that for SiGe HBT;beta increases with V_(be) or I_b, but decreases at I_b < 0.25 mA with I_b, and congregates athigher dose; and a damage factor d(beta) is much less at the same dose for SiGe HBT than for Si BJT.SiGe HBT has much better anti-radiation performance than Si BJT. Some anomalous phenomena forincrease of I_c, I_c -I_(c0), I_b -I_(b0) and beta at low dose have been found. Some electron trapshave been measured. The mechanism of changes of characteristics is discussed.

Difference in electron-and gamma-irradiation effects on output characteristic of color CMOS digital image sensors

Changes of the average brightness and non-uniformity of dark output images,and quality of pictures captured under natural lighting for the color CMOS digital image sensorsirradiated at different electron doses have been studied in comparison to those from theγ-irradiated sensors. For the electron-irradiated sensors, the non-uniformity increases obviouslyand a small bright region on the dark image appears at the dose of 0.4 kGy. The average brightnessincreases at 0.4 kGy, increases sharply at 0.5 kGy. The picture is very blurry only at 0.6 kGy,showing the sensor undergoes severe performance degradation. Electron radiation damage is much moresevere than γ radiation damage for the CMOS image sensors. A possible explanation is presented inthis paper.

Synthesis of GaN films on porous silicon substrates

A novel and simple method was employed to synthesize GaN films on porous silicon （PS） substrates, GaN films were obtained through the reaction between NH3 and Ga2O3 films deposited on the substrates with magnetron sputtering. Since GaN and PS are all good materials for luminescence, it is expected to obtain some new properties from GaN on PS. The samples were analyzed with X-ray diffraction （XRD） to identify crystalline structure. Fourier transmit infrared （FFIR） spectrum was used to analyze the chemical state of the samples. The films were observed with scanning electron microscopy （SEM） and were found to consist of many big crystal grains. Photoluminescence （PL） spectrum was used to illuminate the optical property of the GaN films.

Depletion Mode HEMT with Refractory Metal Silicide WSi Gate

Depletion mode HEMT with refractory metal silicide WSi gate has been designed and fabricated. Epitaxial modulation doping materials were grown by a home-made MBE system. The gate length and width for low noise depletion devices were 1.2-1.5 μm and 2 × 160 μm respectively. The electron mobility of the fabricated devices is typically 6 080 cm2/V.s at 300K and 68 000 cm2/V.s at 77K. The sheet electron concentration ns is 9 × 10 11 cm-2. The source-drain contacts with AuGeNi/Au were fabricated using evaporating and lift-off technique. to further reduce the contact resistance, the wafer was alloyed at 520 ℃ for 3 min in the hydrogen (H2) gas. Schottky gate was formed using WSi. The transconductance of the depletion mode device is 110～130 mS/mm at room temperature. The devices can be applied in communication satellite at microwave frequency of 3. 83 GHz and radar receiver at 1. 5 GHz. Its noise figure is about 2～3 dB.

Amorphous Silicon 16—bit Array Photodetector

Abstract: An amorphous silicon 16 - bit array photodetector with the a - SiC/a -Si heterojunction diode is presented. The fabrication processes of the device were studied systematically. By the optimum of the diode structure and the preparation procedures, the diode with Id< 10 -12 A/mm2 and photocurrent Ip^0.35 A/W has been obtained at the wavelength of 632 nm.

Research of refrigeration system for a new type of constant temperature hydraulic tank

Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of semiconductor refrigeration and establishes a heat transfer model. Semiconductor cooler on piping refrigeration is simulated,and influence of the parameters on the outlet temperature,such as pipe pressure difference of inlet and outlet,pipe length,pipe radius,are gotten,and then hydraulic tank semiconductor refrigeration system is proposed. The semiconductor refrigeration system can control temperature at 37 ± 1°C.

Force Sensing Resistor and Its Applicationto Robotic Control

Abstract: The force sensing resistor (FSR) and its con’struction and characteristic are described. By using the optimal electronic interface, the end result which is a direct proportionality between force and voltage is obtained. The circuits of application for force and position measurements in the robotic control are given. The experiment that FSRs are placed on the fingers of BH - 1 dexterous hand as tactile sensors to measure the contacting forces shows FSR’s force sensitivity is optimized for use in the control of robot contacting with environment.

Diffusion of Zinc in In_xGa_(1-x)As, InP and GaAs

Zinc has been diffused into n-type InxGa1-xAs, InP and GaAs in closed ampoules, and the experimental data for InxGa1-xAs rarely reported previously have been obtained. Theoretically the linear relationship between logarithmic diffusion coefficient InD and the composition x has been demonstrated, which is in good agreement with the experimental results. The calculated diffusion junction depth for InGaAs based on the diffusion model in which D∝ c2 is assumed also agrees well with that of the experiment. Finally the overall diffusion time in a multilayer heterostructure was approximated as t=(Σ )2.

Small Area ROM Design for Embedded Applications

The compact full custom layout design of a 16 kbit mask-programmable complementary metal oxide semiconductor (CMOS) read only memory (ROM) with low power dissipation is introduced. By optimizing storage cell size and peripheral circuit structure, the ROM has a small area of 0.050 mm2 with a power-delay product of 0.011 pJ/bit at +1.8 V. The high packing density and the excellent power-delay product have been achieved by using SMIC 0.18 μm 1P6M CMOS technology. A novel and simple sense amplifier/driver structure is presented which restores the signal full swing efficiently and reduces the signal rising time by 2.4 ns, as well as the memory access time. The ROM has a fast access time of 8.6 ns. As a consequence, the layout design not only can be embedded into microprocessor system as its program memory, but also can be fabricated individually as ROM ASIC.

A study of radiation effects of 9 and 12 MeV protons on Chinese CMOS image sensor degradation

The 9 and 12 MeV proton irradiations of the Chinese CMOS Image Sensor in the fluence range from 1× 10^9 to 4×10^10 cm^-2 and 1 × 10^9 to 2×10^12 cm^-2 have been carried out respectively. The color pictures and dark output images are captured, and the average brightness of dark output images is calculated. The anti-irradiation fluence thresholds for 9 and 12 MeV protons are about 4×10^l0 and 2×10^12 cm^-2, respectively. These can be explained by the change of the concentrations of irradiation-induced electron-hole pairs and vacancies in the various layers of CMOS image sensor calculated by the TRIM simulation program.