In-situ estimation of emission wavelength of embedded InAs QDs using RHEED intensity measurements

Ozaki, Nobuhiko; Ikuno, Daigo

doi:10.1016/j.jcrysgro.2022.126657

Cited by 3 publications

(4 citation statements)

References 27 publications

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“…The inflection point of each function indicates the decay degree of the RHEED intensity. 28) As shown in Fig. 5(b), the thickness at the inflection point varied from 0.74 to 2.54 nm with increasing In composition.…”

Section: Resultsmentioning

confidence: 77%

“…The intensities indicated by the plots were fitted with a curve (solid line) drawn using the Langevin function. 28) We define the critical thickness for the 3D transition as the inflection point of the fitted curve, which is the intersection of the horizontal and vertical dotted lines. The critical thickness for the 3D transition continuously decreased from approximately 1.6-0.9 ML as the value of x increased from 0 to 0.14.…”

Section: Resultsmentioning

confidence: 99%

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In segregation influence on properties of InAs quantum dots in dots-in-a-well

Okuno,

Okada,

Iwaide

et al. 2024

Jpn. J. Appl. Phys.

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We investigated the growth of InAs quantum dots (QDs) in a dots-in-a-well (DWELL) from the perspective of the influence of In segregation from the InGaAs layers in the DWELL. Reflection high-energy electron diffraction (RHEED) measurements during the growth of the lower InGaAs layer indicated that In segregation increased with the In composition of the InGaAs layer. The estimated In segregation values were consistent with the decreases in the critical thickness for the QDs growth and the total volume variations of the grown QDs. These results illustrate that the segregated In from the lower InGaAs layer contributes to the QD growth in the DWELL, and their density increases. Furthermore, RHEED measurements during the growth of the upper InGaAs layer indicated the suppression of the deformation of embedded QDs , which could partially contribute to the longer emission wavelength of the QDs in the DWELL.

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Section: Resultsmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

In segregation influence on properties of InAs quantum dots in dots-in-a-well

Okuno,

Okada,

Iwaide

et al. 2024

Jpn. J. Appl. Phys.

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“…Regarding the growth rate of the LT cover layer, it is kept constant among the four samples, therefore, there is no effect of it on the dot cover growth as reported in Ref. 33. In this study, the effect on the optical properties is brought about by the growth temperature and thickness of the LT cover layer.…”

Section: Mechanism Of the Dislocation Formation In The Cover Layer Of...mentioning

confidence: 70%

Impact of low-temperature cover layer growth of InAs/GaAs quantum dots on their optical properties

Okumura¹,

Fujisawa²,

Naruke³

et al. 2022

Jpn. J. Appl. Phys.

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The effect of low temperature InGaAs/GaAs cover layer growth of InAs quantum dots on its optical and structural properties was investigated. Photoluminescence intensity depended heavily on the growth temperature and thickness of low temperature cover layer and decreased as the number of dislocations formed directly above InAs quantum dots increased. These dislocations are formed at the initial stage of high temperature GaAs growth, originating from pits that remain on the surface after the growth of the low temperature cover layer and subsequent annealing. To ensure a high quality InAs quantum dot structure free from dislocations, it is important to obtain a highly flat surface with suppressed pits after low temperature cover layer growth and subsequent annealing.

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“…的关注 [1][2][3][4][5] 。与传统的量子阱和量子线激光器相比，量子点激光器具有更多优越性，其中包括较低的阈值电流密度，更高的输出功率，更高的工作温度，窄线宽增强因子、抑制侧壁复合率等优势 [6][7][8][9][10][11] 。由于量子点能级是分立的，在低载流子浓度条件下就可以实现粒子数反转，并且量子点中基态载流子的寿命短，可以高效的实现电光转化 [12] 。在体材料中，随着温度升高，载流子会随之连续分布到更高的能量态上。在量子点中的能级存在较大的能量差，这种分立能级能有效地抑制温度造成的载流子在不同能量态上的再分布。因此量子点激光器对温度不敏感 [13] 。此外，量子点激光器中注入的载流子被限制在量子点中抑制了载流子向侧壁扩散从而减少了漏电损失。异质外延有三种生长模式，第一种是二维层状生长，称为 Frank-van der Merwe(F-vdM) 方式，第二种是三维岛状生长，称为 Volmer-Weber(V-W) 方式。第三种是是层状生长加三维成岛生长模式，称为 Stranski-Krastanow(S-K)模式 [14] 。1993年，Leonard 等人首次提出利用分子束外延的生长方法制备应变驱动自组装量子点结构 [15] ，随后量子点激光器在器件性能方面取得了长足的进步，在通信、医学及军事等领域都有极其重要的应用 [16][17][18] 。利用分子束外延技术在 GaAs 上直接制备 InAs 量子点很难将量子点的发光波长拓展至1.31 μm 光通信波段。目前 GaAs 基 InAs 量子点激光器的有源区基本采用 InAs DWELL(dot-in-well) 结构 [19][20][21] ，以该结构作为有源区制备的量子点激光器在1.31 μm 通信波段有广阔的应用前景 [22] 。2021年，牛智川课题组通过短周期超晶格(Short-period superlattice, SPS)生长了 Al x Ga 1-x AsSb 四元数字合金势垒层，制备了高性能的 GaSb 基量子级联激光器 [23] 。2023年，Kumar 等人通过 InAs/InGaAs 短周期超晶格生长的渐变数字合金盖层来释放 InAs 量子点的应变 [24] InAs/GaAs 数字合金超晶格的方式代替常规 InGaAs 层的生长方式可以得到性能良好的激光器。激光器的温度稳定性是衡量激光器性能的重要指标之一。半导体量子点激光器的阈值电流密度与温度成指数关系 [27] ：…”

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Improving structure design of active region of InAs quantum dots by using InAs/GaAs digital alloy superlattice

An-Tian¹,

Ruo-Tao²,

Cao³

et al. 2023

Acta Phys. Sin.

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1.3μm InAs quantum dots lasers have been successfully fabricated on GaAs(100) substrate by molecular beam epitaxy (MBE) using InAs/GaAs digital alloy superlattices instead of the conventional InGaAs layer. The sample grown by conventional growth method and the digital alloy superlattice growth method were characterized by atomic force microscope (AFM) and photoluminescence (PL) spectroscopy. It is found that 8-periods sample have low quantum dot density and poor luminescence performance. With the increase of the number of growth periods, the quantum dot density of the sample increases and the luminous performance improves. This indicated that the quality of the grown sample improves with the increase InAs/GaAs period of the InGaAs layer. When the total InAs/GaAs periods are 32, the quantum dot density of the sample is high and the luminescence performance is good. After the experimental measurement, sample DAL-0 (by conventional growth method) and sample DAL-32 (32-periods InAs/GaAs digital alloy superlattices) were utilized to fabricate quantum dot laser by standard process. The performance of two type quantum dot lasers with different growth methods has been characterized. It is found that the InAs quantum dot lasers fabricated by the sample grown by digital alloy superlattices method have good performances. Under continuous wave operation mode, the threshold current is 24mA corresponding to the threshold current density of 75A/cm<sup>2</sup>. The highest operating temperature reaches 120℃. In addition, InAs quantum dot laser using digital alloy superlattice has good temperature stability. Its characteristic temperature is 55.4K. Compared with the traditional type laser, the InAs quantum dot laser grown by InAs/GaAs digital alloy superlattice has good performance in terms of threshold current density, output power and temperature stability, which indicates that high quality laser can be obtained by this growth method. Using InAs/GaAs digital alloy superlattice growth method, the InGaAs composition can be changed without changing the temperature of the source oven. Thus InAs quantum dot laser with different luminescence wavelength can be obtained through this growth method. InAs/GaAs digital alloy superlattice structure can be adopted to realize different average In content in grown structure. The method provides a new idea for the design and growth of the active region of quantum dot laser.

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In-situ estimation of emission wavelength of embedded InAs QDs using RHEED intensity measurements

Cited by 3 publications

References 27 publications

In segregation influence on properties of InAs quantum dots in dots-in-a-well

In segregation influence on properties of InAs quantum dots in dots-in-a-well

Impact of low-temperature cover layer growth of InAs/GaAs quantum dots on their optical properties

Improving structure design of active region of InAs quantum dots by using InAs/GaAs digital alloy superlattice

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