多变量离子注入型量子阱混杂效应

为实现InP基单片集成光电子器件和系统,对InGaAsP/InGaAsP分别限制异质结多量子阱激光器结构展开量子阱混杂(QWI)技术研究。在不同能量P离子注入、不同快速热退火(RTA)条件以及循环退火下,研究了有源区量子阱混杂技术,实验结果采用光致发光(PL)谱进行表征。实验结果表明:在不同变量下皆可获得量子阱混杂效果,其中退火温度影响最为显著,且循环退火可进一步提高量子阱混杂效果;PL谱蓝移随着退火温度、退火时间和注入能量的增大而增大,退火温度对蓝移的影响最大,在注入剂量为1×10^14 ion/cm2,注入能量为600keV,750℃二次退火150s时获得最大蓝移量116nm。研究结果为未来基于QWI技术设计和制备单片集成光电子器件和系统奠定了基础。     

使用SiO_2介质膜实现InGaAsP量子阱混杂

报道了使用SiO2 介质膜导致的无杂质空位扩散实现InGaAsP多量子阱混杂的实验,得到2 0 0nm的最大带隙波长蓝移.另外,采用量子阱混杂制作了蓝移的FP腔激光器,其性能与未混杂的激光器相当     

光子吸收诱导无序技术的光荧光谱研究

运用 1 0 6 4μm连续输出的Nd∶YAG激光器 ,对与InP晶格匹配的InGaAsP四元系量子阱材料进行了光子吸收诱导无序 (PAID)技术的研究。通过光荧光谱 (PL)的测量 ,证明有量子阱混合现象产生。衬底预加热和聚焦激光束结果表明 ,PAID中辐照时间与衬底温度、辐照的平均功率密度密切相关。聚焦激光照射后的荧光双峰表明PAID有一定的定域处理能力。     

Cu/SiO2逐层沉积增强无杂质空位诱导InGaAsP/InGaAsP量子阱混杂

研究了Cu/SiO_2逐层沉积增强的无杂质空位诱导InGaAsP/InGaAsP多量子阱混杂(QWI)行为。在多量子阱(MQW)外延片表面,采用等离子体增强的化学气相沉积(PECVD)不同厚度的SiO_2,然后溅射5 nm Cu,在不同温度下进行快速热退火(RTA)诱发量子阱混杂。通过光荧光(PL)谱表征样品在QWI前后的变化。实验结果表明,当RTA温度小于700℃时,PL谱峰值波长只有微移,且变化与其他参数关系不大;当RTA温度大于700℃时,PL谱峰值波长移动与介质层厚度和RTA时间都密切相关,当SiO_2厚度为200 nm,退火温度为750℃,时间为200 s时,可获得54.3 nm的最大波长蓝移。该种QWI方法能够诱导InGaAsP MQW带隙移动,QWI效果与InGaAsP MQW中原子互扩散激活能、互扩散原子密度以及在RTA过程中热应力有关。     

Theoretical analysis of the inter-diffusion coefficients in the AlGaInP material quantum well intermixing

Quantum well intermixing (QWI) has been widely used in modifying the bandgap of semiconductor materials, post-growth; it has been investigated in fabricating non-absorbing mirror regions of laser cavities to improve output power. In this work, the QWI mechanism is briefly introduced. A concentration distribution function in multiple quantum wells is mathematically obtained for odd and even wells respectively. In addition, a 650 nm AlGaInP/GaInP quantum well wafer is fabricated by metal organic vapor phase epitaxy, and a series of quantum well intermixing experiments is accomplished by Zn impurity diffusions. Based on experimental data, a concentration distribution function is simulated and an inter-diffusion coefficient between Al and Ga is calculated. Finally, the effects of QWI on the inter-diffusion coefficient are discussed.     

使用SiO2介质膜实现InGaAsP量子阱混杂

报道了使用SiO2介质膜导致的无杂质空位扩散实现InGaAsP多量子阱混杂的实验,得到200nm的最大带隙波长蓝移.另外,采用量子阱混杂制作了蓝移的FP腔激光器,其性能与未混杂的激光器相当.     

InGaAsP/InP Double Quantum Well Intermixing Induced by Phosphorus Ion Implantation

A quantum well intermixing(QWI) investigation on double quantum well(DQW) structure with two different emitting wavelength caused by phosphorus ion implantation and following rapid thermal annealing (RTA) was carried out by means of photoluminescence(PL). The ion implantation was performed at the energy of 120 kev with the dose ranging from 1 × 1011 cm-2 to 1× 1014 cm-2. The RTA was performed at the temperature of 700 ℃ for 30 s under pure nitrogen protection. The PL measurement implied that the band gap blue-shift from the upper well increases with the ion dose faster than that from lower well and the PL peaks from both QWs remained well separated under the lower dose implantation(～1×1011 cm-2 ) indicating that the implant vacancy distribution affects the QWI. When the ion dose is over ～ 1 × 1012 cm-2 , the band gap blue-shift from both wells increases with the ion dose and finally the two peaks merge together as one peak indicating the ion implantation caused a total intermixing of both quantum wells.     

后处理对多孔硅可见光发射的影响

研究了硅单晶表面多孔化后的光致发光现象,特别是多也化以后的后处理对发射光谱分布及强度的影响,以及在激光束照射下的光谱变化,在实验中,我们既观察到发光峰的蓝移,也观察到了红移,实验结果可以用硅量子线的模型解释。     

Quantum-well intermixing in GaAs-AlGaAs structures using pulsed laser irradiation

We report the use of a pulsed laser irradiation technique, using multiphoton absorption, to promote quantum-well intermixing (QWI) in double-quantum-well GaAs-AlGaAs laser structures. The process requires neither ion implantation nor the deposition of dielectric caps. Differential bandgap shifts of up to 40 meV have been obtained between the control and the laser irradiated samples. Bandgap tuned lasers were fabricated from the intermixed samples and exhibited negligible changes in slope efficiency and only small increases (15%) in threshold current compared to as-grown devices.     

Characterizing electric fields in (111)B InGaAs quantum wells using electric field modulated photoluminescence and reflectance techniques

We have performed a series of electroreflectance, photoluminescence, and electric-field-modulated photoluminescence experiments to characterize the strain-induced electric fields in (111)B InGaAs/AlGaAs quantum well p-i-n diode structures. A 180° phase change in the lineshapes of electroreflectance spectra of these samples determines when the quantum well is biased to flatband. Using this bias and a depletion model for the diode, the polarization field in the quantum well can be determined. Contrary to expectations, this polarization field increases significantly with increasing temperature. In addition, at fixed temperature, the quantum well transition energies red-shift with increasing excitation intensity when excited by photons of energy higher than the lowest quantum well transition but lower than the AlGaAs diode's bandgap. When excited with photons of energy greater than the AlGaAs bandgap, the transition energy first red shifts then blue shifts with increasing excitation intensity.     

The effects of laser irradiation on InGaAs/GaAs multiple quantum wells grown by metalorganic molecular beam epitaxy

We studied the effects of Ar ion laser irradiation during the growth of InGaAs/ GaAs multiple quantum wells (MQW) structures by metalorganic molecular beam epitaxy. Structural and optical properties were characterized by Nomarski microscopy, Dektak stylus profiler, and low-temperature photoluminescence (PL) measurements. For MQW structures grown at a relatively low substrate temperature (500°C), the laser irradiation influences greatly the growth process of the In^Ga^^As well and results in a large blue shift of about 2000à in the PL peak. Such a large blue shift suggests that laser modification during growth could have some novel applications in optoelectronics. On the other hand, the laser irradiation has relatively small effects on samples grown at a higher substrate temperature (550°C).     

Growth and photoluminescence study of ZnSe quantum dots

We report detailed photoluminescence (PL) studies of ZnSe quantum dots grown by controlling the flow duration of the precursors in a metal-organic chemical vapor deposition system. The growth time of the quantum dots determines the amount of blue shift observed in the PL measurements. Blue shift as large as 320 meV was observed, and the emission was found to persist up to room temperature. It is found that changing the flow rate and the total number of quantum dot layers also affect the peak PL energy. The temperature dependence of the peak PL energy follows the Varshni relation. From analyzing the temperature-dependent integrated intensity of the photoluminescence spectra, it is found that the activation energy for the quenching of photoluminescence increases with decreasing quantum dot size, and is identified as the binding energy of the exciton in ZnSe quantum dot.     

Impurity-free intermixing in compressively strained InGaAsP multiple quantum well structures

We report on controlled band gap modification in a compressively strained InGaAsP multi-quantum well-laser structure using different encapsulating layers followed by rapid thermal processing (RTP). The structure used was designed as a 1.55 μm laser with an active region consisting of three In_0.76Ga_0.24As_0.85P_0.15 quantum wells with In_0.76Ga_0.24As_0.52P_0.48 barriers grown by metal organic chemical vapor deposition. The heterostructure is capped with 100 nm thick InGaAs layer. Prior to RTP, the samples were coated with various dielectric layers or a thin film of low temperature (300°C) grown InP. Using a Si_xN_y film deposited by plasma-enhanced chemical vapor deposition with a refractive index of about 2.0, quantum well intermixing (QWI) was effectively suppressed. The suppression effect was independent of the Si_xN_y film thickness for layers of 30–2400 nm. With an e-beam-evaporated SiO₂ film, QWI was enhanced and a net blue shift of about 100 nm can be achieved between the samples covered with SiO₂ and Si_xN_y after RTP at 750°C for 100 s. Furthermore, InP grown at a low temperature by gas-source molecular beam epitaxy was proved to be even more efficient in enhancing QWI. Group V interstitial diffusion is used to explain the enhanced QWI between the wells and adjacent barriers which have the same group III compositions. Two-section tunable laser operated around 1.55 μm based on this laser structure was fabricated using this technique.     

Bandgap Engineering in OH‐Functionalized Silicon Nanocrystals: Interplay between Surface Functionalization and Quantum Confinement

In this work, a systematic first‐principles study of the quasi‐band structure of silicon nanocrystals (Si‐NCs) is provided, focusing on bandgap engineering by combining quantum confinement of the electronic states with OH surface‐functionalization. A mapping between the bandgap, Si‐NC diameter, and the degree of hydroxide coverage is provided, which can be used as a guideline for bandgap engineering. Complementary to first‐principles calculations, the photoluminescence (PL) wavelength of Si‐NCs in the quantum‐confinement regime is measured with well‐defined diameters between 1 and 4 nm. The Si‐NCs are prepared by means of a microplasma technique, which allows a surfactant‐free engineering of the Si‐NCs surface with OH groups. The microplasma treatment technique allows us to gradually change the degree of OH coverage, enabling us, in turn, to gradually shift the emitted light in the PL spectra by up to 100 nm to longer wavelengths. The first‐principles calculations are consistent with the experimentally observed dependence of the wavelengths on the OH coverage and show that the PL redshift is determined by the charge transfer between the Si‐NC and the functional groups, while on the other hand surface strain plays only a minor part.     

Carrier-induced energy shift in GaAs/AlGaAs multiple quantum welllaser diodes

Emission energy shift due to high carrier density at threshold in multiple quantum well (MQW) laser diodes is investigated theoretically. This energy shift is evaluated through the Schrodinger and the Poisson equations self-consistently as well as the calculation of the gain spectra with carrier-dependent lifetime broadening. The band filling and the gain broadening effects show a blue shift on the emission energy. Larger number of wells, lower barrier height, or wider well thickness, reduces the blue shift dependence on the carrier density. At high injections, this blue shift is offset by the bandgap shrinkage effect, which displays smaller influence on MQW's. While the carrier density is further increased, the transition due to the second quantized state is found in single quantum wells, however it is difficult to be observed in MQW's     

Proposal of novel gain-levered MQW DFB laser with high andred-shifted FM response

A gain-levered multiple quantum well (MQW) distributed feedback (DFB) laser with high FM efficiency is discussed. The device consists of three sections with different bandgap energy. It can be fabricated by a selective area metalorganic vapor phase epitaxy (MOVPE) growth technique. Numerical analysis shows that a flat, red-shifted, and high FM efficiency of above 1 GHz/mA at 20-mW output power can be realized using the gain levering scheme     

Photoluminescence characteristics of GaN/lnGaN/GaN quantum wells

Photoluminescence (PL) characteristics of GaN/lnGaN/GaN single quantum wells (QWs) and an InGaN/GaN single heterojunction were studied using continuous wave (CW) and pulsed photoluminescence in both edge and surface emitting configurations. Samples were grown on c-plane sapphire substrates by atmospheric pressure metalorganic chemical vapor deposition (MOCVD). Room temperature and 77K PL measurements were performed using a CW Ar-ion laser (305 nm) and a frequency tripled (280 nm), pulsed, mode-locked Ti: sapphire laser. CW PL emission spectra from the quantum wells (24, 30, 80Å) were all blue shifted with respect to the reference sample. The difference (i. e., the blue shift) between the measured value of peak emission energy from the QW and the band-edge emission from the reference sample was attributed to quantum size effects, and to strain arising due to a significant lattice mismatch between InGaN and GaN. In addition, stimulated emission was observed from an InGaN/GaN single heterojunction in the edge and surface emitting configu-ration at 77K. The narrowing of emission spectra, the nonlinear dependence of output emission intensity on input power density, and the observation of a strongly polarized output are presented.     

Auger effect in GaSb quantum well lasers

The Auger recombination effect in GaSb quantum well lasers is discussed. A formula for the calculation of the CHSH Auger rate in quantum well structures is presented, which can be applied to the material where the bandgap is almost the same as the split-off gap. Using this formula, the quantum efficiency of the GaSb quantum well laser is calculated and compared to those of conventional double heterostructure lasers. It is found that the quantum efficiency of the GaSb quantum well laser can be improved to values higher than 50 percent in the wavelength range of1.5-1.8mum.     

Effects of rapid thermal annealing on InAsP/InP strainedmultiquantum well laser diodes grown by metal organic chemical vapourdeposition

The authors report on the effect of rapid thermal annealing (RTA) on the performance of InAsP/InP strained multiquantum well (SMQW) laser diodes (LDs) grown by metal organic chemical vapour deposition. From the photoluminescence (PL) measurements, the optimal RTA temperature for the InAsP/InP strained single quantum well (SSQW) stack was found to be 700°C. The 700°C annealed SSQW stack was found to have a stronger PL peak intensity, no halfwidth broadening and small peak shift, indicating that the degree of interdiffusion of group-V elements can be much reduced. The threshold current and slope efficiency of the 700°C RTA SMQW LDs can be reduced significantly as compared to those of as-grown LDs     

GaAs半导体表面的S-N混合等离子体钝化及在激光器工艺上的应用

利用射频(RF)等离子方法,对GaAs半导体表面进行 了S-N混合等离子体钝化实验,并对工作压强、RF 功率进行了优化。光致发光(PL)测试结果表明,经过S-N混合等离子体钝化的GaAs样品PL 强度提高135%。将本文 钝化方法应用到980nm波长InGaAs应变量子阱(QW)激光器的制备工艺 ,器件的COD阈值功率明显增加。