Peiyi Chen

An improved nonuniformity correction algorithm for infrared focal plane arrays which is easy to implement

An improved nonuniformity correction algorithm is presented which is suitable for infrared focal plane arrays with a nonlinearity of the photoresponse characteristic. Compared to older algorithms, it is simpler, faster and easier to implement by software or hardware. At the same time, it is shown that the correction precision and the correction effect of the new algorithm are substantially the same as that of the old one through theoretical analysis and comparisons of simulation results.

High-quality n-Si/i-p+-i SiGe/n-Si structure grown by ultra high vacuum chemical molecular epitaxy

The n-Si/i-p+-i SiGe/n-Si structure was grown by ultra high vacuum chemical molecular epitaxy, and analysed by high resolution X-ray diffraction, cross-sectional transmission electron microscopy, and secondary ion mass spectroscopy. A high-quality SiGe base layer with an abrupt interface to the Si was obtained. No defects were observed in the n-Si/i-p+-i SiGe/n-Si structure. Both the Ge and boron atoms are uniformly distributed in the p+-SiGe layer, and the changes of profile of both boron and Ge atoms are abrupt from the n-Si to the SiGe layer. A high-performance microwave power SiGe heterojunction bipolar transistor (HBT) was made from the n-Si/i-p+-i SiGe/n-Si structure. Therefore, device-quality n-Si/i-p+-i SiGe/n-Si structures can be grown by ultra high vacuum chemical molecular epitaxy.

Improvement on the performance of P+-GexSi1-x/p-Si heterojunction internal photoemission infrared detectors at 77 K

By using a stacked structure, adding an SiO2 dielectric cavity and an Al mirror, and evaporating a SiO anti-reflecting layer on the back of the substrate, the peak detectivity D-(5.5,D-1000,D-1)* of an unbiased P+-GexSi1-x/p-Si heterojunction internal photoemission (HIP) infrared detector at 77 K has been improved to 1.1 X 10(10) cm Hz(1/2)/W, with a peak quantum efficiency of similar to 2.8% and a photoresponse range of 2-8 mu m. Its D-p* is of the same order of magnitude as that of the PtSi infrared detectors being used in practice. In addition, an improved electrode structure is used in order to improve the performance and reliability of the device

Effects of neutron irradiation on SiGe HBT and Si BJT devices

The change of electrical performance of SiGc HBT and Si BJT is studied after irradiation with 1.3×1013 and 1.0×1014 reactor fast neutrons cm−2. Ic and β decrease, while Ib increases generally with an increasing neutron irradiation fluence for SiGe HBT. For Si BJT, Ic increases at low Vbe bias, decreases at high Vbe bias; Ib increases; and β decreases much more than a SiGe HBT at the same fluence. It is shown that a SiGe HBT has much better anti-radiation performance than a Si BJT. The mechanism of performance changes induced by irradiation is discussed.

Novel strained Si/relaxed SiGe channel PMOSFETs

Abstract Due to the high hole mobility both in the surface strained Si and buried relaxed SiGe channels, we successfully fabricated a novel strained Si/relaxed SiGe channel PMOSFET on the heterostructure strained Si/relaxed SiGe/strained Si/relaxed SiGe buffer layer/grading Si1−xGex layer, grown by home-made UHV/CVD system, which is commonly used in the ‘buried’ SiGe NMOSFET. This device is easier to integrate with SiGe NMOSFET to form SiGe CMOS, than strained SiGe channel PMOSFET. Then the process is presented. With Vgs=3.5 V, the maximum saturated transconductance is found to be twice as large as that of the control Si PMOS, and approximates to that of a traditional strained SiGe channel PMOS.

On the reliability of SiGe microwave power heterojunction bipolar transistor

Although the performance of SiGe heterojunction bipolar transistor has been improved much with the development of epitaxy technology, the reliability is a concern for practical application due to its large mismatch. We have carried out accelerated life test on the SiGe microwave power heterojunction bipolar transistor, and found that the performance of the SiGe microwave power HBT does not change after the HBT is addressed at peak junction temperature of 200/spl deg/C for 168 hrs by forward DC bias. This clearly indicates that the SiGe HBT has the same reliability as Si bipolar transistor.

n-Si/i-p-i SiGe/n-Si structure for SiGe microwave power heterojunction bipolar transistor grown by ultra-high-vacuum chemical molecular epitaxy

The n-Si/i-p-i SiGe/n-Si structure, grown by ultra-high-vacuum chemical molecular epitaxy, was analyzed by cross-sectional transmission electron microscopy and secondary ion mass spectroscopy. It is shown that no defects are observed in the n-Si/i-p-i SiGe/n-Si structure, the interfaces between the SiGe layer and the n-Si layers are clear and planar, both the Ge and boron atoms are uniformly distributed in the p-SiGe, and the profiles of boron and Ge are abrupt from the n-Si to the SiGe layer. A high-performance microwave power SiGe heterojunction bipolar transistor was fabricated using the n-Si/i-p-i SiGe/n-Si structure. Therefore, ultra-high-vacuum chemical molecular epitaxy is one of the most promising methods for the growth of the Si/SiGe strained epilayers.

Ge quantum dot memory realized with vertical Si/SiGe resonant tunneling structure

A modified memory cell using self-assembled Ge quantum dots as float gate is proposed for DRAM application. The vertical structure is strained SiGe channel/n-Si/i-SiGe/n-Si/Ge dots/SiO/sub 2//poly-Si gate. The inside n-Si/i-SiGe/n-Si double barrier acts as tunneling barrier for hole instead of conventional tunneling silicon oxide layer. The function and advantages of the device were analyzed primarily. This novel structure can also be developed to realize non-volatile memory operating at low voltage, if hetero-structure materials system with appropriate band alignment is found.

On the intrinsic spacer layer in Si/SiGe heterojunction bipolar transistor grown by ultra high vacuum chemical vapor deposition

In this paper, we report the study on the intrinsic SiGe spacer layer in Si/SiGe HBT and a novel phenomenon in Si/SiGe HBT layer structure grown by ultra high vacuum chemical vapor deposition (UHVCVD) using Si/sub 2/H/sub 6/ and GeH/sub 4/. When intrinsic SiGe spacer layer width decreases from 100 A to 75 A, the BC junction turn-on voltage decreases from /spl sim/0.6 V to /spl sim/0.2 V, while the BE junction turn-on voltage remains /spl sim/0.6 V. As a result, the offset voltage of the HBT operated at common emitter configuration increases from nearly zero to /spl sim/0.4 V. Therefore, 100 A is used as the intrinsic SiGe spacer layer width. Furthermore, the Si/SiGe HBT layer structures with different SiGe spacer layer widths grown by UHVCVD were investigated by cross-sectional transmission electron microscopy (XTEM). It is shown that a Ge-rich very thin layer exists in the strained SiGe layer grown on Si, which is in parallel with the interface of SiGe and Si. When the SiGe spacer layer width decreases from 100 A to 75 A, the Ge-rich thin layer moves closer to the interface of SiGe base and Si collector, and makes the BC junction turn-on voltage decrease, the offset voltage of HBT, therefore, increases.

Spin-polarized thermionic emission at the interface of ferromagnetic metal and organic semiconductor

We present a model to explain the spin-polarized injection from ferromagnetic metal into organic semiconductor. Thermionic emission mechanism is considered as the dominant transport mechanism at the interface at low bias. Boundary condition is determined from the relationship of the spin-dependent quasi-electrochemical potentials across the interface. The dependences of the current spin polarization on the control parameters, which include the Schottky barrier height at the interface, the spontaneous spin polarization in ferromagnetic metal, and the bias, are demonstrated.