Browsing by Author "Xing, H. G."
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Item Enhanced P-Type Behavior in 2D WSe2 via Chemical Defect Engineering(Institute of Electrical and Electronics Engineers Inc.) Rai, A.; Park, J. H.; Zhang, Chenxi; Kwak, I.; Wolf, S.; Vishwanath, S.; Lin, X.; Furdyna, J.; Xing, H. G.; Cho, Kyeongjae; Kummel, A. C.; Banerjee, S. K.; 0000-0003-2698-7774 (Cho, K); 369148996084659752200 (Cho, K); Zhang, Chenxi; Cho, KyeongjaeDefect engineering of 2D semiconducting transition metal dichalcogenides (TMDCs) has been demonstrated to be a promising way to tune both their bandgaps and carrier concentrations. Moreover, controlled introduction of defects in the source/drain access regions of a TMDC FET can boost its performance by decreasing the contact resistance at the metallTMDC interface [1]. While chemical functionalization offers a facile route towards defect engineering in 2D TMDCs, several chemically-treated TMDCs have not been fully understood at the molecular level. In this study, chemical sulfur treatment (ST) utilizing ammonium sulfide [(NH4)2S] solution is shown to enhance the p-type behavior in 2D WSe2 via introduction of acceptor defect states near its valence band edge (VBE), with the results verified using detailed scanning tunneling microscopy (STM)/spectroscopy (STS) studies, field-effect transistor (FET) measurements and theoretical density-of-states (DOS) calculations.Item Enhanced P-Type Behavior in 2D WSe2 via Chemical Defect Engineering(Institute of Electrical and Electronics Engineers Inc.) Rai, A.; Park, J. H.; Zhang, Chenxi; Kwak, I.; Wolf, S.; Vishwanath, S.; Lin, X.; Furdyna, J.; Xing, H. G.; Cho, Kyeongjae; Kummel, A. C.; Banerjee, S. K.; 0000-0003-2698-7774 (Cho, K); 369148996084659752200 (Cho, K); Zhang, Chenxi; Cho, KyeongjaeDefect engineering of 2D semiconducting transition metal dichalcogenides (TMDCs) has been demonstrated to be a promising way to tune both their bandgaps and carrier concentrations. Moreover, controlled introduction of defects in the source/drain access regions of a TMDC FET can boost its performance by decreasing the contact resistance at the metallTMDC interface [1]. While chemical functionalization offers a facile route towards defect engineering in 2D TMDCs, several chemically-treated TMDCs have not been fully understood at the molecular level. In this study, chemical sulfur treatment (ST) utilizing ammonium sulfide [(NH4)2S] solution is shown to enhance the p-type behavior in 2D WSe2 via introduction of acceptor defect states near its valence band edge (VBE), with the results verified using detailed scanning tunneling microscopy (STM)/spectroscopy (STS) studies, field-effect transistor (FET) measurements and theoretical density-of-states (DOS) calculations.Item Realization of the First GaN Based Tunnel Field-Effect Transistor(Institute of Electrical and Electronics Engineers Inc.) Chaney, A.; Turski, H.; Nomoto, K.; Wang, Qingxiao; Hu, Z.; Kim, Moon J.; Xing, H. G.; Jena, D.; Wang, Qingxiao; Kim, Moon J.Tunnel field-effect transistors (TFETs) offer the means to surpass the subthreshold swing (SS) limit of 60 mV/dec that limits MOSFETs. While MOSFETs rely on modulating a potential barrier, which is subject to a Boltzmann tail in the density of states (DOS), interband tunneling in TFETs enables a sharp turn off of the DOS because the transport is no longer governed by an exponential tail of carriers. These devices have been investigated in Si III-V material systems¹, achieving SS's as low as 20 mV/dec ². GaN is advantageous to these other material systems because its large bandgap is ideal for suppressing leakage current. Unfortunately impurity doping in GaN alone is not enough to achieve the internal fields required to promote interband tunneling[Fig l(a)]. However, by taking advantage of the difference in polarization fields between InGaN and GaN, a device structure favoring interband tunneling can be made [Fig l(b)]. Li et. al.³ have theoretically predicted that a GaN heterojunction TFET could obtain an SS of 15 mV/dec and a peak current of 1× 10⁻⁴ A/µm. For the work being presented, GaN TFETs were fabricated using a surrounding gate (SG) architecture utilizing both nanowires and fins formed from a top-down approach. © 2018 IEEE.