Modelling and simulation of carrier transport in quantum dot memory device for longer data retention and minimized power
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Modelling and simulation of carrier transport in quantum dot memory device for longer data retention and minimized power consumption V. Damodaran1 · Kaustav Choudhury1 · Kaustab Ghosh1 Revised: 25 June 2019 / Accepted: 19 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The performance of a group III–V material quantum dot (QD) nanostructure memory is investigated using a self-consistent Schrödinger solver, eight-band k·p model, and carrier dynamics modelling. This model is used to explore the information loss due to the carrier emission rate in the QDs as a function of temperature, size and confinement potential. The results reveal the dominant emission mechanisms that should occur at different operating temperatures. To minimize the loss and improve the performance at room temperature, our findings reveal an increase in the carrier storage time and a reduction in the power dissipation with increasing dot size. It is further illustrated that electrons are advantageous as information carriers over holes and that the inclusion of high-bandgap barrier layers favours longer-duration data retention. The model is extended to include trap states in realistic QDs, whose effect is found to become more prominent with performance optimization. The computed results are in close agreement with other experimental data for different QDs along with barrier layer. This validates the efficacy of the model, which can be utilized as a design tool for fabricating nanoscale memories with better data retention capability. Keywords Quantum dots · Memory device · Carrier dynamics · Tunnelling emission · Power dissipation · Information storage
1 Introduction Recent years have witnessed considerable research on quantum dots (QDs) for use in a wide variety of applications from optoelectronic devices in photodetectors and lasers to biomedical sensors for cancer cell imaging [1–7]. These nanostructures are also considered to be promising candidates for the fabrication of memory devices that can combine the advantages of both dynamic random-access memory (DRAM) and flash memory [8–13]. This is enabled by the unique features of QDs, such as quantum confinement in three dimensions and a ‘delta-like’ density of states, which results in longer storage and a low escape probability for charge carriers. Although graphene field-effect transistors provide an excellent platform for the development of new-generation flash devices as well as spin-polarized and * Kaustab Ghosh [email protected] 1
School of Electronics Engineering (SENSE), Vellore Institute of Technology, Vandalur Kelambakkam Road, Chennai 600127, India
resistive memories, they exhibit low ON/OFF state contrast due to the zero bandgap, leading to higher read power consumption [14–16]. In this regard, QD-based devices are better candidates for memory applications due to the ability to flexibly tune the localization energy by varying the material combination and QD size, and incorporating a high-bandgap barrier material. QD memories are rep
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