Front pages with contents of No. 53, 1994

Front cover. Contents.

Back pages of No. 53, 1994

Charles Darwin Foundation for the Galapagos Islands. Map.

Euskal literatura Gernika aldizkari liberalean :1945-53

[EU]Liburuak erbesteratutako idazleen lanak aztertzen ditu, bereziki euskarazkoak. Gernika aldizkaria Gerra Zibiletik ihesi joandakoen biltokia izan zen Euskal Herrian. Aztertzen da modernitatea nola joan zen agertuz Gernika aldizkarian hiru belaunalditan, Octavio Pazen "Los hijos del limo" liburuko modernitatearen deskribapenaren laguntzaz. Horrez gain, aldizkariaren ibilbidea jasotzen da.

Humanism after the Spanish Civil War: Gernika (1945-53), a Humanities and Social Sciencesbasque magazine

Espainiako Gerra Zibilaren eta II. Mundu Gerrarren ostean Gerra Hotza heldu zen. Testuinguru larri horretan humanismoan ikusi zuten hainbatek zibilizazio-krisiari irtenbidea topatzeko bidea. Gernika aldizkariak (1945-53) bere burua humanistatzat zeukan. Bertako idazleek gai horren inguruan zer adierazi zuten jasotzen saiatu gara, euskarazko zein erdarazko artikuluetan agertzen diren iritziak sailkatuz.

Enhancement of 1.53 mu m photoluminescence from spin-coated Er-Si-O (Er2SiO5) crystalline films by nitrogen plasma treatment

Er-Si-O (Er2SiO5) crystalline films are fabricated by the spin-coating and subsequent annealing process. The fraction of erbium is estimated to be 21.5 at% based on Rutherford backscattering measurement. X-ray diffraction pattern indicates that the Er-Si-O films are similar to Er2SiO5 compound in the crystal structure. The fine structure of room-temperature photoluminescence of Er3+-related transitions suggests that Er has a local environment similar to the Er-O-6 octahedron. Our preliminary results show that the intensity of 1.53 mu m emission is enhanced by a factor of seven after nitrogen plasma treatment by NH3 gas with subsequent post-annealing. The full-width at half-maximum of 1.53 pm emission peak increases from 7.5 to 12.9 nm compared with that of the untreated one. Nitrogen plasma treatment is assumed to tailor Er3+ local environment, increasing the oscillator strength of transitions and thus the excitation/emission cross-section. (c) 2005 Elsevier B.V. All rights reserved.

Evaluating 0.53 eVGaInAsSbthermophotovoltaic diode based on an analytical absorption model

Radiant heat conversion performance dominated by the active layer of Ga0.84In0.16As0.14Sb0.86 diode has been systematically investigated based on an analytic absorption spectrum, which is suggested here by numerically fitting the limited experimental data. For the concerned diode configuration, our calculation demonstrates that the optimal base doping is 3-4 x 10(17) cm(-3), which is less sensitive to the variation of the external radiation spectrum. Given the scarcity of the alloy elements, an economical device configuration of the 0.2-0.6 mu m emitter and the 4-6 mu m base would be particularly acceptable because the corresponding conversion efficiency cannot exhibit discouraging degradation in comparison to the one for the optimal structure, the thickness of which may be up to 10 mu m. More importantly, the method we suggested here to calculate alloy absorption can be easily transferred to other composition, thus bringing great convenience for design or optimization of the optoelectronic device formed by these alloys.

In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As量子阱中的正磁电阻效应

在低温强磁场条件下,对In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As量子阱中的二维电子气进行了磁输运测试.在低磁场范围内观察到正磁电阻效应,在高磁场下这一正磁电阻趋于饱和,分析表明这一现象与二维电子气中的电子占据两个子带有关.在考虑了两个子带之间的散射效应后,通过分析低磁场下的正磁电阻,得到了每个子带电子的迁移率,结果表明第二子带电子的迁移率高于第一子带电子的迁移率.进一步分析表明,这主要是由两个子带之间的散射引起的.

两个子带占据的In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As量子阱中填充因子的变化规律

研究了低温(1.5K)和强磁场(0-13T)条件下,InP基In_(0.53)Ga_(0.47)As/In_(0.52)A_(l0.48)As量子阱中电子占据两个子带时填充因子随磁场的变化规律.结果表明,在电子自旋分裂能远小于朗道能级展宽的情况下,如果两个子带分裂能是朗道分裂能的整数倍时,即⊿E_(21)=κ*ω_c(其中κ为整数),填充因子为偶数;当两个子带分裂能为朗道分裂能的半奇数倍时,即⊿E_(21)=(2κ+1*ω/2,填充因子出现奇数.

In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As量子阱中双子带占据的二维电子气的输运特性

研究了不同沟道厚度的In_(0.53) Ga_(0.47)As/In_(0.52)Al_(0.48)As量子阱中双子带占据的二维电子气的输运特性.在考虑了两个子带电子之间的磁致子带间散射效应后,通过分析Shubnikov-de Haas振荡一阶微分的快速傅里叶变换结果,获得了每个子带电子的浓度、输运散射时间、量子散射时间以及子带之间的散射时间.结果表明,对于所研究的样品,第一子带电子受到的小角散射更强,这与第一子带电子受到了更强的电离杂质散射有关.

不同量子阱宽度的InP基In_(0.53)GaAs/In_(0.52)AlAs高电子迁移率晶体管材料二维电子气的性能研究

用Shubnikov-de Haas(SdH)振荡效应,研究了在1.4 K下不同量子阱宽度(10-35 nm)的InP基高电子迁移率晶体管材料的二维电子气特性.通过对纵向电阻SdH振荡的快速傅里叶变换分析,得到不同阱宽时量子阱中二维电子气各子带电子浓度和量子迁移率.研究发现,在Si掺杂浓度一定时,阱宽的改变对于量子阱中总的载流子浓度改变不大,但是随着阱宽的增加,阱中的电子从占据一个子带到占据两个子带,且第二子带上的载流子迁移率远大于第一子带迁移率.当量子阱宽度为20 nm时,处在第二子能级上的电子数与处在第一子能级上的电子数之比达到了最大值0.24.此时有最多的电子位于迁移率高的第二子能级,材料的迁移率也最大.此结果对于优化器件的设计有重要意义.

匹配In（0.53）Ga（0.47）As/InP量子阱材料的GSMBE生长及特性分析

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