Ge组分对SiGe HBT直流特性的影响

制作了基区Ge组分分别为0.20和0.23的多发射极指数双台面结构SiGe异质结双极型晶体管(HBT).实验结果表明,基区Ge组分的微小增加,引起了较大的基极复合电流,但减小了总的基极电流,提高了发射结的注入效率,电流增益成倍地提高.Ge组分从0.20增加到0.23,HBT的最大直流电流增益从60增加到158,提高了约2.6倍.

A double wavelength DFB laser with an identical active area for CWDM

A novel distribute feedback (DFB) laser which gave two different wavelengths under two distinct work conditions was fabricated. The laser consists of two Bragg gratings with different periods corresponding to wavelength spacing of 20 nm in an identical active area. When driving current was injected into one of the different sections separately, two different wavelengths at 1542.4 and 1562.5 nm were realized. The side mode suppression ratio (SMSR) of 45 dB or more both for the two Bragg wavelengths were achieved. The fabricating process of the laser was just the same as that of traditional DFB laser diode. This device can be potentially used in coarse wavelength division multiplexer (CWDM) as a promising light source and the technology idea can be used to enlarge the transmission capacity in metro area network (MAN).

An Improved Driving Circuit for Thermo-Optical Switch to Improve the Reliability of Thermo-Optical Switch Matrix

The influence of the heaters on the reliability of the thermo-optic (TO) switch matrix is analyzed and an improved driving circuit based on the analyzed results is designed and fabricated. The circuit can improve the reliability of the switch matrix device from 78.87% to 97.04% for a 4×4 optical switch device with a simplified tree structure. The simulation and experimental results show the circuit can provide suitable driving current for TO switch matrix.

扫描隧道显微镜对InAs/GaAs自组织生长量子点的准原位研究

报道了用MBE-SPM联合系统对InAs/GaAs量子点进行准原位研究的初步结果。STM图像表明，在对n~+-GaAs衬底进行脱氧处理后，通过生长GaAs缓冲层能有效的改善表面质量。在缓冲层上继续生长2单原子层InAs后形成了量子点。SPM与透射电子显微镜给出的量子点形貌的异同在文中也给出了合理的解释，该研究工作的进一步深入将对自组织生长量子点的生长机理的理解和样品质量的提高有重要意义。

Growth and characterization of GaN on LiGaO2 and LiAlO2

The nearly lattice-matched LiGaO2 and LiAlO2 substrates have been used for the growth of GaN by LP-MOVPE. GaN epilayers have been grown on the two substrates at very low input partial pressure of hydrogen and relatively low growth temperature. The difference in the growth rate, crystal and optical qualities of hexagonal GaN epilayers grown on LiAlO2 and LiGaO2 substrate with two polar domains are investigated. LiAlO2 and LiGaO2 single crystal with a single domain structure and an adequate surface plane are promising substrates for the growth of high quality of hexagonal GaN thin films.

Energy band and acceptor binding energy of GaN and AlxGa1-xN

The hole effective-mass Hamiltonian for the semiconductors of wurtzite structure is established, and the effective-mass parameters of GaN and AlxGa1-xN are given. Besides the asymmetry in the z and x, y directions, the linear term of the momentum operator in the Hamiltonian is essential in determining the valence band structure, which is different from that of the zinc-blende structure. The binding energies of acceptor states are calculated by solving strictly the effective-mass equations. The binding energies of donor and acceptor for wurtzite GaN are 20 and 131, 97 meV, respectively, which are inconsistent with the recent experimental results. It is proposed that there are two kinds of acceptors in wurtzite GaN. One kind is the general acceptor such as C, substituting N, which satisfies the effective-mass theory, and the other includes Mg, Zn, Cd etc., the binding energy of which deviates from that given by the effective-mass theory. Experimentally, wurtzite GaN was grown by the MBE method, and the PL spectra were measured. Three main peaks are assigned to the DA transitions from the two kinds of acceptor. Some of the transitions were identified as coming from the cubic phase of GaN, which appears randomly within the predominantly hexagonal material. The binding energy of acceptor in ALN is about 239, 158 meV, that in AlxGa1-xN alloys (x approximate to 0.2) is 147, 111 meV, close to that in GaN. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

典型污染海湾河口沉积物中砷的形态分布研究

锦州湾是我国较大的浅水海湾之一，该湾西南五里河沿岸汇集数家工厂排污直接人海， 形成该湾口处的最大污染源。其西南部潮滩地段已成为我国海域污染最严重的区域之一。 本文对葫芦岛3条河流、五里河口和锦州湾水体、沉积物中As的含量、分布、形态及行为进行了系统研究。结果表明，葫芦岛的连山河和五里河未受到明显的As污染，沉积物总As含量一般低于10 mg•kg-1，河水As含量一般低于10 μg•L-1，茨山河下游紧邻葫芦岛锌厂，受到了严重的As污染，沉积物As含量达75.2 mg•kg-1。五里河口区As污染非常严重，锌厂在该区排污口处沉积物As含量高达3176.1 mg•kg-1，超过国家沉积物As标准158倍。受锌厂排污的影响锦州湾As污染也很严重，沉积物中As最高含量达到569.5 mg•kg-1。沉积物和孔隙水As含量在剖面上具有相似的变化趋势，表明孔隙水As含量主要受沉积物As含量影响。锦州湾沉积物中As主要以可交换态存在，残渣态次之，盐酸提取态最少，表明锦州湾沉积物中As的活性很强，有大量的可交换态As随时会进入上覆水体，是重要的As释放源，沉积物中大量As的释放可能会对葫芦岛和锦州湾地区生态系统造成严重的威胁。 以盐度和酸碱度作为环境影响因子进行的释放模拟实验，结果显示：不同盐度条件下，沉积物中的As均在48h左右达到最大释放量。此时，盐度为0‰的水体中As的释放量最大，而其他两种盐度的水体中As的释放量较小且二者相差不大。另外，在室温条件下，随着pH值的升高，沉积物中As的释放量逐渐增加。 通过对不同形态的单一含砷矿物的As提取效果研究得出：对于分级提取方法中吸附态砷的最佳提取条件应为1M KH2PO4 (pH5) 24h, 无定型铁氧化物上结合的砷0.2M oxalic/oxalate (pH3)避光 6h, 硫化亚铁上结合的砷，0.2M oxalic/oxalate (pH3)避光 1h。