Quantum Dots for Optoelectronic Devices - Phdassistance

1. QuantumDots for Optoelectronic Devices An Academic presentationby Dr. Nancy Agnes, Head, Technical Operations,Phdassistance Group www.phdassistance.com Email:info@phdassistance.com

2. TODAY'SDISCUSSION Outline Introduction Research advancements in quantum dots Futurescope

3. INTRODUCTION Nanometre-scale semiconductor chips have been imagined as next-generation technologywithhigh functionality andconvergence. Quantum dots, also known as artificial atoms, have special properties owing to their quantum confinement in all threedimensions. Quantum dots have a lot of interest in optoelectronic systems because of their special properties. Contd...

4. Many attempts have been made worldwide to improve the efficiency and functionality of these promising nanomaterials for next-generation optoelectronic devices like lasers, photodetectors, amplifiers, and solarcells. Quantum dot devices with outstanding performance surpassing prior devices have been demonstrated by producing optoelectronic devices based on quantum dots over the last two decades. The progress in quantum dots for optoelectronic devices has been described in this article over the last fewyears.

5. RESEARCH ADVANCEMENTSIN QUANTUMDOTS For decades, self-assembled nanostructures have been a topic of considerable concern andsignificance. By shrinking the dimensions of a semiconductor to a nanoscale, certain special properties, such as quantum effects, can beobtained. The electrical and optical properties of nanometre-sized semiconductors can bemanipulated by manipulating their morphology, thanks to the quantum scaleeffect. Contd...

6. Semiconductor quantum dots (QDs), similar to electrons, are a fascinating nanoscale structure of confined carriers in alldimensions. Compared to conventional bulk semiconductors, 0D semiconductor nanostructures are more tuneable and sensitive to externalparameters. Furthermore, since QDs are zero-dimensional, they have distinct energy levels and a density of states that can be reduced to a set of deltafunctions. Low-dimensional semiconductors have gained a lot of interest because of their fundamentaladvantages. Contd...

7. discovered wavelength theoretically This can be observed in the 1970s; Dingle and Henry quantum-organized semiconductor lasers could achieve tunability and threshold reduction [1], which was later demonstrated in the 1980 s by Asada et al. and Arakawa et al.[ 2 ] . Since there was no feasible fabrication technique for QDs for several years after these pioneering works , the efforts dedicated to QDs and their implementations in devices were only experimentalresearch. Due to major advancements in epitaxial development techniques, self- assembled QDs were impossible to make until the early1990 s. Contd...

8. After self- assembled QDs were successfully fabricated, laser diodes based on QDs running at 77 K were quickly developed. Following the good demonstration of self- assembled QDs and the f i rst QD laser, a worldwide initiative was launched to improve QD growth control and manufacture high- performance laser chips. The majority of researchon self- assembled QDs focuses on material structures with mismatched lattices, such as In(Ga)As/GaAs[3]andInAs/InP[4]. Contd...

9. Thermodynamic arguments are often used to explain heteroepitaxial growth modes in thin films. The improvement made in QD self-assembly was quickly rewarded. Quantum dot infrared photodetectors (QDIPs) [3], quantum dot solar cells (QDSCs) [5], quantum dot superluminescent diodes (QDSLDs) [6], and quantum dot amplifiers [7] have all been documented, in addition to lasers. The invention of mid-wavelength and long-wavelength infrared photodetectors [5] was prompted by inter-subband absorption in QDs in the late 1990s. Contd...

10. Several groups published QDSCs, quantum dot amplifiers, and QDSLDs in the 2000s. The work on optimizing material growth and product architecture is still going on to deliver on the promise of high-performance QD optoelectronic products. As seen in figure 1, the threshold current density of QD lasers has recently reached the highest value for QW lasers produced for many decades.

11. Figure 1. The record threshold current densities at the time of publication can be seen in the historical history of heterostructure lasers[8].

12. FUTURESCOPE Since these nanostructures were first grownand categorized, self-organized quantumdot optoelectronic devices have come a longway. Quantum dot lasers are now on par with quantum well lasers in terms ofefficiency. Inter-sublevel instruments, which can beused as light sources and detectors and canoperate in a surface-normal mode, haveincreased efficiency and specialproperties. Contd...

13. Quantum dot optoelectronic sensors are expected to play a major role in upcoming systems. High-performance QDIPs are also possible thanks to the intensive research activities inQDs. QDIPs have basic benefits over Quantum Well Infrared Photodetector (QWIP) in thatthey can run at higher temperatures and have lower darkcurrent. QDIPs are now outperforming QWIPs in terms of efficiency. QDIPs haveoutperformed QWIPs in terms of operatingtemperature. Several issues remain, such as inadequate quantum performance, and QDIParchitecture and fabrication must be enhanced to realize their potential in third-generation infrared sensing. Contd...

14. QDIPs with efficiency comparable to existing state-of-the-art technologiessuch asQWIPs and HgCdTe photodetector may be used in the comingyears. Due to various fundamental shortcomings, such as QDs' slow absorption and the extreme thermal connection between the intermediate and conduction bands, QDSCs are theleast evolved of the various forms of QD optoelectronicsystems. Further advances in device physics, design, growth, and characterization of QDSCswould be needed to achieve high conversion efficiency beyond the record value of GaAs single- junction solarcells.

15. CONTACTUS UNITEDKINGDOM +44 7537144372 INDIA +91-9176966446 EMAIL info@phdassistance.com