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Piezoreflectance study of GaAs/AlGaAs digital alloy compositional graded heterostructures
Published in Jong-Chun Woo, Yoon Soo Park, Compound Semiconductors 1995, 2020
D Y Lin, F C Lin, Y S Huang, H Qiangt, F H Pollak, D L Mathine, G N Maracas
Graded band-gap material is of great importance in band-gap engineering and is widely used in high speed optical modulators, photodetectors, and laser diodes, etc. Although rectangular quantum wells (RQWs) have been extensively employed as active regions of opto-electronic devices, they have certain limitations. The symmetrical rectangular quantum wells (SRQW) have an overlap integral between the fundamental conduction and heavy-hole wave functions that are very close to unity when no electric field is applied. However, in most opto-electronic devices the quantum well is subjected to internal and external fields from the device. These fields cause a spatial separation of electron and hole wave functions that decreases the overlap integral between the conduction-band and valence-band wave functions. A reduction in the overlap integral implies a reduction in the emission or absorption processes. To overcome the decrease in the overlap integral, novel quantum well designs such as those containing compositional gradients are deployed. Recently, arbitrary shaped quantum wells have been implemented by molecular beam epitaxy (MBE) in such devices with an emphasis on the study of asymmetric triangular quantum wells (ATQWs) [1-5]. These quantum well structures have demonstrated their potential in increasing the overlap integrals. Thus there is considerable interest in studying the properties of samples fabricated by the digital alloy compositional grading (DACG) method.
Sonochemical Synthesis of Mg-Doped Zno NPS For Efficient Sunlight Driven Photocatalysis
Published in Bharat A. Bhanvase, Rajendra P. Ugwekar, Raju B. Mankar, Novel Water Treatment and Separation Methods, 2017
S. P. Meshram, P. D. Jolhe, S. D. Shingte, B. A. Bhanvase, S. H. Sonawane
Several modification methods have been developed to improve the photocatalytic activity of ZnO. Band gap engineering is one of the most important approaches involved in designing optically and electrically confined structures. Several researchers have attempted a transition metal and anionic doping to improve the photocatalytic activity of ZnO.10−12 Still, surplus charge carrier recombination limits the practical applications of these transition metal- and anion-doped ZnO. Optionally, II-VI compounds like magnesium oxide (MgO) having high optical band gap can be used for alloying ZnO to increase its band gap, owing to small lattice mismatch of MgO with ZnO. It has been reported that, the band gap can be considerably tuned from 3.3 to 7.8 eV for wurtzite and cubic structured Ziy.Mg.O, by simply varying the Mg content.13 Although, solubility limits of Mg in ZnO is low (about ~4 at%%), it largely depend on the synthesis techniques and the processing conditions.14 Accordingly, several researchers have reported different techniques to intricate Ziy.Mg.O, namely sol-gel method, chem ical vapor deposition, pulsed laser deposition, spray pyrolysis, molecular beam epitaxy (MBE), radio frequency (RF) magnetron sputtering, electro- deposition, and metal-organic vapor-phase epitaxy (MOVPE).15−22
not metals
Published in DAVID K. FERRY, Semiconductor Transport, 2016
In all of the discussion above, it was assumed that the alloy can be grown lattice matched to a suitable substrate. Is this what one wants to do? Certainly, it has been argued that one should try to lattice match the heterojunction interface so as not to introduce defects and dislocations arising from release of local strain. On the other hand, it has been found in non- lattice-matched heterostructures that there is a critical thickness of the overgrown layer, below which the strain is not released. Rather, the grown layer is distorted so that its lattice constant along the interface matches the substrate. This results in a distortion of the basic cubic cell in that the cell is compressed (extended) along the interface and therefore is extended (compressed) in the direction normal to the interface (or vice versa depending upon which lattice constant is larger). Yet these layers can be grown quite easily with modem growth techniques such as molecular-beam epitaxy or metal- organic vapor-phase epitaxy. The resulting "strained-layer heterojunction" is a high-quality interface in which the lattice of the grown layer is purposely mismatched to that of the substrate. The layer can be grown as long as it is sufficiently thin (here, this is usually thought to be of the order of 20 nm or less) (Matthews and Blakeslee, 1974). The reason for doing this lies in the dependence of the band structure on the lattice constant. The built-in strain modifies the band structure to produce desirable properties as part of the overall concept of band-gap engineering.
Radiation study of TFET and JLFET-based devices and circuits: a comprehensive review on the device structure and sensitivity
Published in Radiation Effects and Defects in Solids, 2023
As already known, MOSFET has limitations in subthreshold swing (SS) and it cannot be reduced below 60 mV/dec so there arises the need to explore steep slope electronic devices (49,50). High drive current (ION), lower SS and less leakage current (IOFF) are the important metrics for any device to be used for low-power applications (51). For ultra-low power applications, Tunnelling Field Effect Transistor (TFET) is used as an alternative to CMOS with the reduced supply voltage giving a lesser SS of 53 mv/dec (52,53). TFET using adaptive band gap engineering reduces SS and has lesser leakage current (54). Barrier-controlled TFET uses different work functions for providing lesser OFF current and higher ON current (55). TFET shows a shorter transient current pulse and smaller collected charge as parasitic bipolar effects are suppressed when heavy ion radiation of 10 MeVcm2/mg strikes the center of the channel during the OFF state (56).
Robustness in half-metallicity, thermophysical and structural properties of Co2YAl (Y = Pd, Ag) Heuslers: a first-principles perspective
Published in Molecular Physics, 2022
Ashwani Kumar, Saurabh Singh, Shakeel Ahmad Sofi, Tarun Chandel, Naveen Thakur
There are two aspects of spintronics in the context of current efforts in band gap engineering. The first is to develop devices with high spin polarisation [14–16] to improve spin filtering [17]. The second is a more prominent, emphasising on devising advanced ways for the generation and utilisation of spin-polarised current. These essential aspects include searching in semiconductors for spin transport so that they may be utilised as spin-valve [18] and spin polarisers [19]. Heusler alloys exhibit identical crystallographic structures, multifunctional characteristics and certain similar electronic structural profiles [20–22]. Such robust characteristics make them highly appreciable in the context of the present study. Profound demand for half metals holding high Curie temperature [23–26] is more practical and researchers are working to discover such novel materials.
Cap layer effect in DC and RF characteristics of InP based n-p-n metamorphic δ-doped heterojunction bipolar transistor
Published in International Journal of Electronics Letters, 2022
M. R. Jena, A. Diwarkar, A. K. Panda, G. N. Dash
The Gummel plots for the InP/InGaAs-based n-p-n HBT having InGaAs cap is shown in Figure 4 both for the simulated as well as experimental device. The simulated HBT exhibits a maximum DC current gain (β) of 255 which is exactly equal to the experimentally measured value (Tsai et al., 2012). In addition, the curves for the simulated device have a fairly good agreement with those of the fabricated device (Tsai et al., 2012). These findings are thus indicative of the fact that our model used closely follows the experimental device. Overall, our model can thus be considered to stand a good validation. Next we change the cap layer to the quaternary material and compute the DC gain. The results for the two cap layers are shown in Figure 5. The HBT with quaternary cap has witnessed a substantial augmentation in the DC gain recording a maximum value of 300 as against the same of 255 for the ternary cap. The concepts of band gap engineering as applied in this case thus stand authenticated.