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Yongsik Kim,Minkyung Bae,Woojoon Kim,Dongsik Kong,Hyun Kwang Jung,Hyungtak Kim,Sunwoong Kim,Dong Myong Kim,Dae Hwan Kim IEEE 2012 IEEE transactions on electron devices Vol.59 No.10
<P>A combination of the multifrequency <I>C</I>- <I>V</I> and the generation-recombination current spectroscopy is proposed for a complete extraction of density of states (DOS) in amorphous InGaZnO thin-film transistors (a-IGZO TFTs) over the full subband-gap energy range (<I>EV</I> ≤ <I>E</I> ≤ <I>EC</I>) including the interface trap density between the gate oxide and the a-IGZO active layer. In particular, our result on the separate extraction of acceptor- and donor-like DOS is noticeable for a systematic design of amorphous oxide semiconductor TFTs because the former determines their dc characteristics and the latter does their threshold voltage (<I>VT</I>) instability under practical operation conditions. The proposed approach can be used to optimize the fabrication process of thin-film materials with high mobility and stability for mass-production-level amorphous oxide semiconductor TFTs.</P>
Choi, Sungju,Kang, Youngjin,Kim, Jonghwa,Kim, Jungmok,Choi, Sung-Jin,Kim, Dong Myong,Cha, Ho-Young,Kim, Hyungtak,Kim, Dae Hwan The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.5
It is essential to acquire an accurate and simple technique for extracting the interface trap density ($D_{it}$) in order to characterize the normally-off gate-recessed AlGaN/GaN hetero field-effect transistors (HFETs) because they can undergo interface trap generation induced by the etch damage in each interfacial layer provoking the degradation of device performance as well as serious instability. Here, the frequency-dependent capacitance-voltage (C-V) method (FDCM) is proposed as a simple and fast technique for extracting $D_{it}$ and demonstrated in normally-off gate-recessed AlGaN/GaN HFETs. The FDCM is found to be not only simpler than the conductance method along with the same precision, but also much useful for a simple C-V model for AlGaN/GaN HFETs because it identifies frequency-independent and bias-dependent capacitance components.
Sungju Choi,Youngjin Kang,Jonghwa Kim,Jungmok Kim,Sung-Jin Choi,Dong Myong Kim,Ho-Young Cha,Hyungtak Kim,Dae Hwan Kim 대한전자공학회 2015 Journal of semiconductor technology and science Vol.15 No.5
It is essential to acquire an accurate and simple technique for extracting the interface trap density (Dit) in order to characterize the normally-off gate-recessed AlGaN/GaN hetero field-effect transistors (HFETs) because they can undergo interface trap generation induced by the etch damage in each interfacial layer provoking the degradation of device performance as well as serious instability. Here, the frequency-dependent capacitance-voltage (C-V) method (FDCM) is proposed as a simple and fast technique for extracting Dit and demonstrated in normally-off gate-recessed AlGaN/GaN HFETs. The FDCM is found to be not only simpler than the conductance method along with the same precision, but also much useful for a simple C-V model for AlGaN/GaN HFETs because it identifies frequency-independent and biasdependent capacitance components.
Kim, Myeong-Ho,Lee, Young-Ahn,Kim, Jinseo,Park, Jucheol,Ahn, Seungbae,Jeon, Ki-Joon,Kim, Jeong Won,Choi, Duck-Kyun,Seo, Hyungtak American Chemical Society 2015 ACS NANO Vol.9 No.10
<P>The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal–OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm<SUP>2</SUP> V<SUP>–1</SUP> sec<SUP>–1</SUP>, the carrier concentration at ∼10<SUP>20</SUP> cm<SUP>–3</SUP> without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-10/acsnano.5b05342/production/images/medium/nn-2015-053422_0007.eps'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5b05342'>ACS Electronic Supporting Info</A></P>
AlGaN/GaN-on-Si Power FET with Mo/Au Gate
Kim, Hyun-Seop,Jang, Won-Ho,Han, Sang-Woo,Kim, Hyungtak,Cho, Chun-Hyung,Oh, Jungwoo,Cha, Ho-Young The Institute of Electronics and Information Engin 2017 Journal of semiconductor technology and science Vol.17 No.2
We have investigated a Mo/Au gate scheme for use in AlGaN/GaN-on-Si HFETs. AlGaN/GaN-on-Si HFETs were fabricated with Ni/Au or Mo/Au gates and their electrical characteristics were compared after thermal stress tests. While insignificant difference was observed in DC characteristics, the Mo/Au gate device exhibited lower on-resistance with superior pulsed characteristics in comparison with the Ni/Au gate device.
Kim, Hyun-Seop,Eom, Su-Keun,Seo, Kwang-Seok,Kim, Hyungtak,Cha, Ho-Young Elsevier 2018 Vacuum Vol.155 No.-
<P><B>Abstract</B></P> <P>This paper reports the first-time evaluation of the time-dependent dielectric breakdown of recessed AlGaN/GaN-on-Si metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with plasma enhanced chemical vapor deposition (PECVD) SiO<SUB>2</SUB> gate oxide. The interface fixed charge density and oxide bulk charge density extracted from the flat-band voltage characteristics were 2.7 × 10<SUP>11</SUP> ± 6.54 × 10<SUP>10</SUP> cm<SUP>−2</SUP> and -9.71 × 10<SUP>17</SUP> ± 5.18 × 10<SUP>16</SUP> cm<SUP>−3</SUP>, respectively. The time dependent dielectric breakdown (TDDB) characteristics exhibited longer lifetime estimation as the SiO<SUB>2</SUB> thickness increased. The excellent reliability of the PECVD SiO<SUB>2</SUB> film was validated for use as the gate oxide of recessed AlGaN/GaN MOS-HFET.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We reports the TDDB characteristics of recessed AlGaN/GaN-on-Si MOS-HFETs with PECVD SiO<SUB>2</SUB> gate oxide for the first time. </LI> <LI> We observed that the PECVD SiO<SUB>2</SUB> films had negative net bulk charges. </LI> <LI> The interface fixed charge density and oxide bulk charge density were 2.4 × 10<SUP>11</SUP> cm<SUP>−2</SUP> and -9.71 × 10<SUP>17</SUP> cm<SUP>−3</SUP>, respectively. </LI> <LI> The TDDB characteristics exhibited longer lifetime estimation as the SiO<SUB>2</SUB> thickness increased. </LI> </UL> </P>