Singlemode 1.55 /spl mu/m VCSELs with low threshold and high output power

The continuous-wave room-temperature operation of an electrically pumped 1.55 /spl mu/m wavelength vertical-cavity surface-emitting laser (VCSEL) with up to 1.7 mW output power is reported. The laser comprises an optimised multi-quantum-well active region and an improved mirror design for reduced optical losses.     

Polarisation control in VCSELs by elliptic surface etching

850 nm-wavelength vertical-cavity surface-emitting lasers (VCSELs) with an elliptical shallow surface relief having various aspect ratios and orientations have been fabricated. Using appropriate etch dimensions, VCSELs of up to 12.5 μm active diameter are forced to operate on the fundamental mode for a certain current range. By aligning the longer axis of the etched ellipse with the [011] or [011¯] crystal axis, the polarisation of the fundamental mode is pinned accordingly with a polarisation suppression ratio of ~30 dB     

Single fundamental-mode output power exceeding 6 mW from VCSELs with a shallow surface relief

A single fundamental-mode output power of 6.5 mW was achieved from an 850-nm vertical-cavity surface-emitting laser (VCSEL) with a shallow surface relief, the highest single-mode power ever reported using this technique. The VCSELs were fabricated from epitaxial material grown to yield an antiphase reflection from the topmost layer. A circular surface relief, acting as a mode discriminator, was etched in the center to reduce the mirror loss for the fundamental mode. This "inverted" surface-relief technique offers relaxed etch depth control and, therefore, improves reproducibility and yield.     

Influence of spatial hole burning on the output power of a CW dye ring laser

The output power of a single-mode CW dye ring laser can be enhanced by 50 percent by changing over from standing-wave (SW) operation to traveling-wave (TW) operation. This effect is attributed to smoothing out the SW pattern in the active medium, which gives rise to spatial inhomogeneities of the inversion.     

Experimental demonstration of spatial hole burning reduction leading to 1480-nm pump lasers output power improvement

Observation of spatial hole burning reduction is reported for the first time to our knowledge on flared 1480-nm high-power InGaAsP-InP buried ridge lasers. We determined the longitudinal carrier density profile by spatially resolved spontaneous emission measurements for slightly tapered and straight active waveguides. The tapered stripe shows spatial hole burning reduction leading to 25% output power enhancement.     

High singlemode output power from long-wavelength VCSELs using curved micro-mirrors for mode control

Concave curved micro-mirrors enable record high 2.8 mW singlemode emission from long-wavelength vertical-cavity surface-emitting lasers with large current apertures up to 12 /spl mu/m. Higher-order transverse modes are suppressed by more than 48 dB, while polarisation control by a dominating mirror asymmetry is demonstrated after coupling 1.9 mW into a singlemode fibre.     

VCSELs based on arrays of sub-monolayer InGaAs quantum dots

Vertical-cavity surface-emitting lasers (VCSELs) with an active region based on sub-monolayer InGaAs quantum dots and doped AlGaAs/GaAs distributed Bragg reflectors were grown by MBE. VCSELs with current aperture of 3 μm in diameter demonstrate single-mode lasing in 980-nm range with the threshold current of 0.6 mA, maximum output power up to 4 mW, and external differential efficiency of 68%. Multimode VCSELs with a (10–12)-μm aperture demonstrate ultralow internal optical loss of 0.09% per pass, which compares favorably with the best results obtained in similar lasers with undoped distributed Bragg reflectors. Original Russian Text ? S.A. Blokhin, N.A. Maleev, A.G. Kuz’menkov, Yu. M. Shernyakov, I.I. Novikov, N.Yu. Gordeev, V.V. Dyudelev, G.S. Sokolovskiĭ, V.I. Kuchinskiĭi, M.M. Kulagina, M.V. Maximov, V.M. Ustinov, A.R. Kovsh, S.S. Mikhrin, N.N. Ledentsov, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 633–638.     

大功率垂直腔表面发射激光器的新进展

介绍了垂直腔面发射激光器研究进展.重点介绍了激光器在效率,输出功率、光束质量、温度特性等方面的新成果.探讨了大功率垂直腔面发射激光器在工业、医疗、国防等领域的应用.     

Dynamics of spectral hole burning

A model calculation is presented that describes the features of spectral-hole burning measurements performed under conditions of femtosecond transient excitation and probing. Pump-induced changes in the spectrum of probe transmittance arise not only from changes in level population (hole burning), but also from the presence of pump polarization during the probe, and from perturbations of the decay of the probe polarization. These latter effects give rise to oscillating differential transmittance spectra when the (shorter) probe pulse arrives prior to the peak of the pump noise. Only when the probe pulse follows the bulk of the pump pulse does the level population effect dominate the spectrum, so that one can observe dynamic hole-burning effects without distortion     

过孔刻蚀工艺优化对过孔尺寸减小的研究

为了适应TFT-LCD小型化与窄边框化以及在面板布线精细化的趋势,提高工艺设计富裕量以及增加面板的实际利用率,之前做过钝化层沉积工艺优化来减小液晶面板阵列工艺中连接像素电极与漏极的过孔尺寸的研究。本文在此基础上进行过孔刻蚀工艺的优化,从而最终达到进一步减小过孔尺寸实现TFT-LCD小型化与窄边框化的趋势。通过设计实验考察了影响过孔大小刻蚀主要影响因素(功率、压强、气体比率、刻蚀速率选择比)。实验结果表明,在薄膜沉积优化的基础上可使过孔的尺寸再降低10%~20%。对其进行了良率检测与工艺稳定性评价,最终获得了过孔尺寸减小的方案,并成功导入到产品生产中,从而提高了产品品质。     

Gain saturation enhancement of longitudinal hole burning viastanding wave induced wave coupling in a semiconductor laser

It is shown by a simple theoretical model that the large scale longitudinal hole burning in a semiconductor laser will enhance by about 2.6 times the gain saturation caused by the cavity standing wave induced wave coupling     

Measurements of the InGaAs hole impact ionization coefficient inInAlAs/InGaAs pnp HBTs

The hole multiplication factor in pnp InAlAs/InGaAs single heterojunction bipolar transistors (HBTs) has been measured as a function of the base-collector bias. The hole impact ionization coefficient β_p has been estimated taking into account the Early effect, I_CBO, and thermal effects. Numerical corrections for dead space were made. The importance of considering second order effects is highlighted, showing that rough approximations can lead to an overestimation of the coefficient β_p. At low electric fields, the extracted coefficient agrees with the most recent photomultiplication measurements available in the literature. At high electric fields, hole impact ionization coefficient is estimated up to values previously not reported in the literature (β_p≈10⁴ cm^-1)     

Enhanced output power in GaN-based LEDs with naturally textured surface grown by MOCVD

GaN-based light-emitting diodes (LEDs) with naturally textured surfaces grown by MOCVD were demonstrated. In this study, a growth-interruption step and a surface treatment using biscyclopentadienyl magnesium (CP/sub 2/Mg) were simultaneously performed to form a plurality of nuclei sites on the surface of a p-type cladding layer, and then a p-type contact layer was grown on the p-type cladding layer, so as to create a p-type contact layer with a rough surface having truncated pyramids. Experimental results indicated that GaN-based LED with the truncated pyramids on the surface exhibited an enhancement in output power of 66% at 20 mA. It is worth noting that the typical 20-mA-driven forward voltage is only slightly higher than those of conventional LEDs (without the Mg-treatment process).     

ICP刻蚀InGaAs的微观损伤机制研究

为获得低损伤、稳定性好的感应耦合等离子体（ICP）刻蚀InGaAs探测器台面成型工艺,采用Raman光谱技术和X射线衍射（XRD）技术,初步研究了Cl2/N2气氛刻蚀InGaAs的主要损伤机制,确定以晶格缺陷损伤为主;并采用微波反射光电导衰退（-PCD）法对不同处理工艺下表面的缺陷损伤进行了表征和分析,结果表明刻蚀表面湿法腐蚀和硫化的方法可在一定程度上减小表面的缺陷损伤和断键,但是存在一些深层次的缺陷。     

Er-fibre lasers: suppression of spatial hole burning by internal modulation

Spatial hole burning is suppressed in linear Er/sup 3+/ fibre lasers by two alternative modulation schemes. They move the standing wave pattern, formed by the two counterpropagating waves, along the gain medium in an oscillatory or continuous way. Output bandwidths <5 kHz result.<>     

Fabrication of InP/InGaAs photodiodes for high bit rate communication by reactive ion etching

It is shown that reactive ion etching can be used for mesa etching and selfaligned contact cap removal in InP/InGaAs photodiode fabrication, without inducing unacceptable diode leakage currents. Mesa diodes with approximately 100 nA leakage, 90% quantum efficiency, and 12 GHz bandwidth at 5 V bias and 1.3 mu m wavelength, and pairs and quadruplets of such detectors for coherent lightwave systems are demonstrated.<>     

Performance optimization of InGaAs power LDMOSFET

In this paper, a power laterally diffused metal-oxide-semiconductor field-effect transistor (LDMOSFET) on InGaAs is proposed to achieve substantial improvement in breakdown voltage, on-resistance and Baliga׳s figure-of-merit with reduced cell pitch. The proposed LDMOSFET contains two vertical gates which are placed in two separate trenches built in the drift region. The source and drain contacts are taken from the top. The modified device has a planer structure implemented on InGaAs which is suitable for medium voltage power integrated circuits. The performance of proposed device is evaluated using two-dimensional numerical simulations and results are compared with that of the conventional LDMOSFET. The proposed structure considerably reduces the electric field inside the drift region due to reduced-surface field (RESURF) effect even at increased doping concentration leading to improved design trade-off. The proposed device provides 144% higher breakdown voltage, 25% lower specific on-resistance, 8 times improvement in figure-of-merit, and 25% reduction in cell pitch as compared to the conventional device.     

Enhanced characteristics in gate-recessed and sidewall-recessed AlGaAs/InGaAs PHEMTs by citric-based selective wet etching

Improved device performance in Al_0.2Ga_0.8As/In_0.15Ga_0.85As gate-recessed enhancement-mode pseudomorphic high electron mobility transistors (E-PHEMTs) and sidewall-recessed depletion-mode PHEMTs (D-PHEMTs) using a newly developed citric buffer etchant are reported. The innovated etchant near room temperature (23°C) possesses a high GaAs/Al_0.2Ga_0.8As or In_0.15Ga_0.85As/Al_0.2Ga_0.8As etching selectivity (>250) applied to an etched stop surface. For E-PHEMTs, the transconductance (G_m) of 315?mS/mm and high linearity of 0.46?V-wide gate voltage swing (drop of 10% peak G_m), corresponding to 143?mA/mm-wide I_DS, even at a gate length of 1?µm is obtained. For microwave operation, this 1?µm-gate E-PHEMT shows the f_max (maximum operation frequency) of 29.2?GHz and the f_T (cut-off frequency) of 11.2?GHz, respectively. The measured minimum noise figure (NF_min), under V_DS?=?3?V and I_DS?=?7.5?mA, is 0.56?dB at 1?GHz with the associated gain of 10.86?dB. The NF_min is less than 1.5?dB in the frequency range from 1 to 4?GHz. In addition, an effective and simple method of selective gate sidewall recess is utilized to etch the low barrier in In_0.15Ga_0.85As channel at mesa sidewalls for D-PHEMTs. For D-PHEMTs with 1?×?100?µm² exhibit a very low gate leakage current of 2.4?μA/mm even at V_GD?=??10?V and high gate breakdown voltage over 25?V. As compared to that of no sidewall recess, nearly two orders of reduction in magnitude of gate leakage current and 100% improvement in gate breakdown voltage are achieved.     

Self-compensation of short-channel effects in sub-0.1-μmInAlAs/InGaAs MODFETs by electrochemical etching

We show that by making full use of the features of electrochemical etching in InAlAs/InGaAs heterostructures, deep gate grooves with small side etching can be fabricated. The most important advantage of this technology is that the vertical etching in the small gate openings will be remarkably enhanced by a self-organized process. Therefore the electrochemical etching provides a what we call “self-compensation” of the short channel effects. The effectiveness of this technology is evidenced by the excellent performance combined with the alleviation of the threshold-voltage shift and suppression of transconductance degradation in MODFET's with gate lengths below 0.1 μm