量子阱无序的窗口结构InGaAs/GaAs/AlGaAs量子阱激光器

对ＳｉＯ２薄膜在快速热退火条件下引起的空位诱导ＩｎＧａＡｓ／ＧａＡｓ应变量子阱无序和ＳｒＦ２薄膜抑制其量子阱无序的方法进行了实验研究。并将这两种技术的结合（称为选择区域量子阱无序技术）应用于脊形波导ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变量子阱激光器，研制出具有无吸收镜面的窗口结构脊形波导量子阱激光器。该结构３μｍ条宽激光器的最大输出功率为３４０ｍＷ，和没有窗口的同样结构的量子阱激光器相比，最大输出功率提高了３６％。在１００ｍＷ输出功率下，发射光谱中心波长为９７８ｎｍ，光谱半宽为１．２ｎｍ。平行和垂直方向远场发散角分别为７．２°和３０°     

分子束外延GaAs／AlGaAs超晶格缓冲层量子阱材料的研究

采用分子束外延技术生长了ＧａＡｓ／ＡｌＧａＡｓ单量子阱得多量子阱材料。采用ＧａＡｓ／ＡｌＧａＡｓ超晶格缓冲层掩埋衬底缺陷，获得的量子阱结构材料被成功地用于制作量子阱激光器。波长为７７８ｎｍ的激光器，最低阈值电流为３０ｍＡ，室温下线性光功率大于２０ｍＷ。     

应变InGaAs／AlGaAs量子阱激光器的工作特性

人们对激射波长在０．９＜λ＜１．１μｍ的应变ＩｎＧａＡｓ／ＡｌＧａＡｓ量子阱（ＱＷ）激光器很感兴趣。主要应用有泵浦晶体或玻璃主体中的稀土离子（特别是掺Ｅｒ３＋光纤放大器的９８０ｎｍ泵浦），研制透明衬底的面发射激光器和增加倍频二极管激光器的可用波长范围。本文叙述了多种结构应变ＩｎＧａＡｓ／ＡｌＧａＡｓ单量于阱激光器的工作特性。     

GaAs／Al_xGa_（1－x）As多量子阱掩埋条形激光器

利用ＭＢＥ生长的ＧａＡｓ／ＡｌｘＧａ１－ｘＡｓ折射率渐变－分别限制－多量子阱材料（ＧＲＩＮ－ＳＣＨ－ＭＱＷ），经液相外延二次掩埋生长，制备了阈值最低达２．５ｍＡ（腔面未镀膜），光功率室温连续输出可达１５ｍＷ／面的半导体激光器．经腔面镀膜后，器件已稳定工作４５００多小时．     

InGaAs/GaAs/AlGaAs应变量子阱激光器

优化设计了既能实现较小垂直方向远场发散角,又能降低腔面光功率密度的ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变层量子阱激光器,并计算了该结构激光器实现基横模工作的脊形波导结构参数。利用分子束外延生长了ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变量子阱激光器材料并研制出基横模输出功率大于１４０ｍＷ,激射波长为９８０ｎｍ的脊形波导应变量子阱激光器,其微分量子效率为０．８Ｗ／Ａ,垂直和平行结平面方向远场发散角分别为２８°和６．８°     

GaAlAs／GaAs量子阱LD泵浦Nd：YAG激光器

利用分子束外延技术生长出了ＧａＡｌＡｓ／ＧａＡｓ折射率渐变分别限制单量阱材料。用该材料作出的激光二极管作泵浦源对Ｎｄ：ＹＡＧ激光器进行端面泵浦实验，在工作电流为３．３Ａ时，ＬＤ输出功率为２．７Ｗ，得到Ｎｄ：ＹＡＧ激光器的输出功率达７００ｍＷ，光－光转换效率达２０％。     

低阈值基横模脊形波导GaAs／AlGaAs单量子阱激光器

本文报道了脊形波导结构ＧａＡｓ／ＡｌＧａＡｓ量子阱激光器的研究成果．我们采用湿法化学腐蚀方法，通过对器件结构参数的优化，制备了性能优越的脊形波导ＧａＡｓ／ＡｌＧａＡｓ量子阱激光器，器件的阈值电流低于１０ｍＡ，最低值为７．３ｍＡ，而且实现了基横模工作，这是国内报道的该结构激光器的最好水平．     

MBE生长温度对InGaAs／GaAs应变单量子阱激光器性能的影响

采用分子束外延（ＭＢＥ）技术，研制生长了ＩｎＧａＡｓ／ＧａＡｓ应变单量子阱激光器材料，并研究了生长温度及界面停顿生长对激光器性能的影响。结果表明，较高的ＩｎＧａＡｓ生长温度和尽可能短的生长停顿时间，将有利于降低激光器的阈值电流。所外延的激光器材料在２５０μｍ×５００μｍ宽接触、脉冲工作方式下测量的阈电流密度的典型值为１６０ｍＡ／ｃｍ２。用湿法腐蚀制作的４μｍ条宽的脊型波导激光器，阈值电流为１６ｎＡ，外微分量子效率为０４ｍＷ／ｍＡ，激射波长为９７６±２ｎｍ，线性输出功率为１００ｍＷ。     

MBE生长高质量GaAs／AlGaAs量子阱激光器

我们利用分子束外延方法研制了ＧａＡｓ／ＡｌＧａＡｓ缓交折射率分别限制（ＧＲＩＮ－ＳＣＨ）单量子阱和双量子阱激光器．对腔长为６００μｍ的端面不镀膜的宽接触条型Ｆ－Ｐ腔激光器，阈值电流密度（平均值）分别为２９０Ａ／ｃｍ２和２４０Ａ／ｃｍ２．腔长在１２００μｍ的双量子阱激光器的阈电流密度低达１９０Ａ／ｃｍ２．对出光面和背面分别镀以增透膜和高反膜的宽接触条型（８０μｍ）．激光器，线性输出功率高达１．８２Ｗ；出光面的斜率效率达到１．０４Ｗ／Ａ；利用湿法化学腐蚀所制备的脊形波导结构单量子阱激光器阈值电流最低可达８ｍＡ     

GaAs／AlxGa1—xAs多量子阱掩埋条形激光器

利用ＭＢＥ生长的ＧａＡＡｌｘＧａ１－ｘＡｓ折射率渐变－分别限制－多量子阱材料（ＧＲＩＮ－ＳＣＨ－ＭＱＷ），经液相一次掩埋生长，制备了阈值最低达２．５ｍＡ（腔面未镀膜），光功率室温连续输出可达１５ｍＷ／面的半导体激光器，经腔面多功能摹一器件已稳定工作４５００多小时。     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.     

Electrooptic ferroelectric Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films

We report on waveguiding and electrooptic properties of epitaxial Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films grown by radio-frequency magnetron sputtering on Al/sub 2/O/sub 3/(11_02) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.     

A 1 cm/spl times/1 cm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 1 cm/spl times/1 cm array of 100 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APD). The average breakdown voltage was 28.7 V with a standard deviation of less than 0.5 V. The distribution of breakdown voltage across the area followed a radial pattern consistent with a slight epitaxial growth nonuniformity. The mean dark current at a gain of 10, or 6.1 A/W, was 10.3 nA, and none of the 100 APDs had a dark current of more than 25 nA. The bandwidth at a gain of 10 was 6.2 GHz, and the maximum gain-bandwidth product was 140 GHz. This technology is ideally suited for next-generation three-dimensional imaging applications.