Comparison for 1/ <tex> ${f}$</tex> Noise Characteristics of AlGaN/GaN FinFET and Planar MISHFET

Vodapally, Sindhuri,Theodorou, Christoforos G.,Bae, Youngho,Ghibaudo, Gerard,Cristoloveanu, Sorin,Im, Ki-Sik,Lee, Jung-Hee IEEE 2017 IEEE transactions on electron devices Vol.64 No.9

<P>DC and 1/f noise performances of the AlGaN/GaN fin-shaped field-effect transistor (FinFET) with fin width of 50 nm were analyzed. The FinFET exhibited approximately six times larger normalized drain current and transconductance, compared to those of the AlGaN/GaN planar metal-insulator-semiconductor heterostructure field-effect-transistor (MISHFET) fabricated on the same wafer. It was also observed that the FinFET exhibited improved noise performance with lower noise magnitude of 8.5x10(-15) A(2)/Hz when compared to the value of 8.7x10(-14)A(2)/Hz for the planar MISHFET. An intensive analysis indicated that both devices follow the carrier number fluctuation model, but the FinFET suffers much less charge trapping effect compared to the MISHFET (two orders lower charge trapping was observed). Moreover, the FinFET did not exhibit the Lorentz-like components, which explains that the depleted fin structure effectively prevents the carriers from being trapped into the underlying thick GaN buffer layer. On the other hand, the slope of the noise is 2 irrespective of drain voltage and apparently showed the Lorentz-like components, especially at high drain voltage in MISHFET device. This explains that the carrier trapping/detrapping between the 2-D electron gas channel and the GaN buffer layer is significant in MISHFET.</P>

1/f-Noise in AlGaN/GaN Nanowire Omega-FinFETs

Vodapally, Sindhuri,Jang, Young In,Kang, In Man,Cho, In-Tak,Lee, Jong-Ho,Bae, Youngho,Ghibaudo, Gerard,Cristoloveanu, Sorin,Im, Ki-Sik,Lee, Jung-Hee IEEE 2017 IEEE electron device letters Vol.38 No.2

<P>The low-frequency noise (LFN) characteristics of AlGaN/GaN FinFETs with omega-gate and combined two-dimensional electron gas (2DEG) and MOS conduction are investigated. It is found that LFN is dominated by carrier number fluctuations whatever the width of the fin. Charge trapping in narrow devices is one order of magnitude lower than in wide fin device. In narrow devices, the sidewall conduction prevails and the noisemainly stems fromthe carrier trapping in the sidewall Al2O3 gate dielectric. Instead, in wide fin devices, the top gate AlGaN/GaN HEMT structure dominates and the LFN is mostly governed by the carrier trapping in the GaN layer close to 2DEG channel.</P>

Device Performances Related to Gate Leakage Current in Al₂O₃/AlGaN/GaN MISHFETs

Do-Kywn Kim,V.Sindhuri,Dong-Seok Kim,Young-Woo Jo,Hee-Sung Kang,Young-In Jang,In Man Kang,Youngho Bae,Sung-Ho Hahm,Jung-Hee Lee 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.5

In this paper, we have characterized the electrical properties related to gate leakage current in AlGaN/GaN MISHFETs with varying the thickness (0 to 10 nm) of Al₂O₃ gate insulator which also serves as a surface protection layer during high-temperature RTP. The sheet resistance of the unprotected TLM pattern after RTP was rapidly increased to 1323 Ω/□ from the value of 400 Ω/□ of the as-grown sample due to thermal damage during high temperature RTP. On the other hand, the sheet resistances of the TLM pattern protected with thin Al₂O₃ layer (when its thickness is larger than 5 nm) were slightly decreased after high-temperature RTP since the deposited Al₂O₃ layer effectively neutralizes the acceptor-like states on the surface of AlGaN layer which in turn increases the 2DEG density. AlGaN/GaN MISHFET with 8 nmthick Al₂O₃ gate insulator exhibited extremely low gate leakage current of 10<SUP>-9</SUP> A/mm, which led to superior device performances such as a very low subthreshold swing (SS) of 80 mV/dec and high Ion/Ioff ratio of ~ 1010. The PF emission and FN tunneling models were used to characterize the gate leakage currents of the devices. The device with 5 nm-thick Al₂O₃ layer exhibited both PF emission and FN tunneling at relatively lower gate voltages compared to that with 8 nm-thick Al₂O₃ layer due to thinner Al₂O₃ layer, as expected. The device with 10 nm-thick Al₂O₃ layer, however, showed very high gate leakage current of 5.5 ×10<SUP>-4</SUP> A/mm due to poly-crystallization of the Al₂O₃ layer during the high-temperature RTP, which led to very poor performances.

Device Performances Related to Gate Leakage Current in Al₂O₃/AlGaN/GaN MISHFETs

Kim, Do-Kywn,Sindhuri, V.,Kim, Dong-Seok,Jo, Young-Woo,Kang, Hee-Sung,Jang, Young-In,Kang, In Man,Bae, Youngho,Hahm, Sung-Ho,Lee, Jung-Hee The Institute of Electronics and Information Engin 2014 Journal of semiconductor technology and science Vol.14 No.5

In this paper, we have characterized the electrical properties related to gate leakage current in AlGaN/GaN MISHFETs with varying the thickness (0 to 10 nm) of $Al_2O_3$ gate insulator which also serves as a surface protection layer during high-temperature RTP. The sheet resistance of the unprotected TLM pattern after RTP was rapidly increased to $1323{\Omega}/{\square}$ from the value of $400{\Omega}/{\square}$ of the as-grown sample due to thermal damage during high temperature RTP. On the other hand, the sheet resistances of the TLM pattern protected with thin $Al_2O_3$ layer (when its thickness is larger than 5 nm) were slightly decreased after high-temperature RTP since the deposited $Al_2O_3$ layer effectively neutralizes the acceptor-like states on the surface of AlGaN layer which in turn increases the 2DEG density. AlGaN/GaN MISHFET with 8 nm-thick $Al_2O_3$ gate insulator exhibited extremely low gate leakage current of $10^{-9}A/mm$, which led to superior device performances such as a very low subthreshold swing (SS) of 80 mV/dec and high $I_{on}/I_{off}$ ratio of ${\sim}10^{10}$. The PF emission and FN tunneling models were used to characterize the gate leakage currents of the devices. The device with 5 nm-thick $Al_2O_3$ layer exhibited both PF emission and FN tunneling at relatively lower gate voltages compared to that with 8 nm-thick $Al_2O_3$ layer due to thinner $Al_2O_3$ layer, as expected. The device with 10 nm-thick $Al_2O_3$ layer, however, showed very high gate leakage current of $5.5{\times}10^{-4}A/mm$ due to poly-crystallization of the $Al_2O_3$ layer during the high-temperature RTP, which led to very poor performances.

Performance of AlGaN/GaN Nanowire Ω-Shaped-Gate Fin-Shaped Field-Effect Transistor

Lee, Dong-Gi,Sindhuri, V.,Jo, Young-Woo,Son, Dong-Hyeok,Kang, Hee-Sung,Lee, Jae-Hong,Lee, Jae-Hoon,Cristoloveanu, Sorin,Im, Ki-Sik,Lee, Jung-Hee American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5

Fabrication of AlGaN/GaN Ω-shaped nanowire fin-shaped FETs by a top-down approach

Im, Ki-Sik,Sindhuri, Vodapally,Jo, Young-Woo,Son, Dong-Hyeok,Lee, Jae-Hoon,Cristoloveanu, Sorin,Lee, Jung-Hee JAPAN SOCIETY OF APPLIED PHYSICS 2015 Applied physics express Vol.8 No.6

<P>An AlGaN/GaN-based Omega-shaped nanowire fin-shaped FET (FinFET) with a fin width of 50 nm was fabricated using tetramethylammonium hydroxide (TMAH)-based lateral wet etching. An atomic layer deposited (ALD) HfO2 side-wall layer served as the etching mask. ALD Al2O3 and TiN layers were used as the gate dielectric and gate metal, respectively. The Omega-shaped gate structure fully depletes the active fin body and almost completely separates the depleted fin from the underlying thick GaN buffer layer, resulting in superior device performance. The top-down processing proposed in this work provides a viable pathway towards gate-all-around devices for III-nitride semiconductors. (C) 2015 The Japan Society of Applied Physics</P>

Early initiation of breastfeeding and factors associated with its delay among mothers at discharge from a single hospital

Mary J. Jenifer Florence,Sindhuri R.,Kumaran A. Arul,Dongre Amol R. 대한소아청소년과학회 2022 Clinical and Experimental Pediatrics (CEP) Vol.65 No.4

Background: According to the National Family Health Survey– 4, in India, 78.9% of deliveries occur in institutions, although only 42.6% of new mothers initiate breastfeeding within 1 hour of delivery.Purpose: To estimate the proportion of early initiation of breastfeeding (EIBF) among new mothers at discharge from a tertiary care hospital and identify the determinants of delayed initiation of breastfeeding among them.Methods: This was a hospital-based analytical cross-sectional study of 108 new mothers. After obtaining Institutional Review Board approval and informed consent, we interviewed the new mothers on the day of discharge. Multivariate logistic regression was performed using IBM SPSS Statistics ver. 24.Results: The median breastfeeding initiation time was 90 minutes (interquartile range, 30–180 minutes). Overall, 43.5% of the mothers practiced EIBF, 77.4% practiced exclusive breastfeeding, and 43.5% were rooming in at discharge. Reasons for breastfeeding delays included extended recovery time from spinal anesthesia, maternal lassitude, and uncomfortable breastfeeding position due to post-cesarean pain. In the multivariate analysis, a birth weight less than 2,500 g (adjusted odds ratio [aOR], 4.33; 95% confidence interval [CI], 1.12–16.82; P=0.03), cesarean section delivery (aOR, 4.68; 95% CI, 1.57– 13.92; P=0.005), and mother’s poor knowledge of breastfeeding (aOR, 4.61; 95% CI, 1.44–14.72; P=0.010) were more likely to delay the initiation of breastfeeding.Conclusion: EIBF was practiced by less than half of the new mothers as determined by the cesarean section, baby’s birth weight, and mothers’ awareness of breastfeeding. Thus, it is vital to improve breastfeeding and nutritional counseling among mothers during the antenatal period and improve healthcare professionals’ training to facilitate EIBF, even in circumstances such as cesarean section.

Effects of Electroacupuncture on the Regulation of Chemokine Induced Spinal Activation of Microglia in the Rat Model of Neuropathic Pain

비슈누몰라칼라 신드후리,이지은,박혜지,김소희,구성태,Sindhuri, Vishnumolakala,Lee, Ji Eun,Park, Hye-Ji,Kim, So-Hee,Koo, Sungtae Society for Meridian and Acupoint 2019 대한침구의학회지 Vol.36 No.4

Objectives : Microglia play a crucial role in electroacupuncture (EA) analgesia on neuropathic pain. The role of chemokines in producing analgesic effects of EA, however, is largely unknown. In the present study, we investigated the role of chemokines in producing analgesic effects of EA in the neuropathic pain model. Methods : Sprague-Dawley rats were randomly assigned into three groups (anesthetized group (ANE), non-acupoint EA group (NAP), and ST36 - GB34 EA group (ACU)). Neuropathic pain was induced by tight ligation of L5 spinal nerve. Mechanical and thermal hypersensitivity of hind paw was tested. Western blot tests and immunofluorescence assay for C-C motif chemokine ligand 2 (CCL2) levels and microglia activation were performed on spinal cord L5/6. EA was treated once daily from the 3rd day after surgery for 5 days. Results : EA treatments applied to ST36 and GB34 significantly reduced both mechanical and thermal hypersensitivity after two and three times of treatment, respectively. While CCL2 expression significantly increased in neuropathic rats, it was significantly reduced in the ACU. In addition, co-localization of CCL2 and activated microglia significantly decreased in the ACU compared to those of ANE and NAP in the spinal cord L5/L6 dorsal horn. Conclusions : The present results suggest that EA applied to ST36 and GB34 modulates the reduction of CCL2 release from the injured neurons and consequently decreases microglia activation in the spinal cord. Regulation of chemokine induced spinal activation of microglia plays a key role in analgesic effects of EA in the rat model of neuropathic pain.

Capacitance-voltage characterization of Al₂O₃/GaN-on-insulator (GaNOI) structures with TMAH surface treatment

Im, Ki-Sik,Kim, Jeong-Gil,Vodapally, Sindhuri,Caulmilone, Raphaë,l,Cristoloveanu, Sorin,Lee, Jung-Hee ELSEVIER 2017 MICROELECTRONIC ENGINEERING Vol.178 No.-

<P><B>Abstract</B></P> <P>The capacitance-voltage (<I>C-V</I>) characterizations of Al<SUB>2</SUB>O<SUB>3</SUB>/GaN-on-insulator (GaNOI) structure, prepared with the Smart Cut™ technology, with and without tetramethylammonium hydroxide (TMAH) surface treatment have been investigated. The GaNOI structure consists of a 150nm-thick GaN layer and a 800μm-thick Si<SUB>3</SUB>N<SUB>4</SUB>/SiO<SUB>2</SUB> buried insulating layer deposited on sapphire substrate. For fabrication of the MIS capacitor, an Al<SUB>2</SUB>O<SUB>3</SUB> layer with thickness of 28nm as a gate dielectric was deposited on the GaNOI wafer by atomic layer deposition (ALD). The calculated carrier concentration of the GaN layer on the buried insulator was increased to 2.8×10<SUP>17</SUP> cm<SUP>−3</SUP> from the value of ~5×10<SUP>16</SUP> cm<SUP>−3</SUP> for the as-grown undoped GaN layer prior to the wafer transfer. The MIS capacitor with TMAH surface treatment showed a positive threshold voltage shift with negligible hysteresis and low interface trap density compared to the capacitor without TMAH surface treatment. Severe frequency dispersion was observed regardless of the TMAH treatment due to the crystal defects generated during the complicated wafer transfer process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Al<SUB>2</SUB>O<SUB>3</SUB>/GaN-on-insulator (GaNOI) capacitors were fabricated using TMAH surface treatment. </LI> <LI> The calculated doping density of GaN layer was obtained to 2.8×10<SUP>17</SUP> cm<SUP>−3</SUP>. </LI> <LI> This capacitors exhibited the severe frequency dispersion due to the crystal damaged GaN layer. </LI> <LI> The TMAH surface-treated MIS capacitor showed better performances compared to the TMAH-free device. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>