Impact of Work Function Tunability on Thermal and RF Performance of P-type Window based Junctionless Transistor

THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH Impac o Wo k Func ion Tunabili y on The mal and RF Pe o mance o P- ype Window Based Junc ionless T ansis o P iyansh TRIPATHI 1, Na end a YADAVA2, Mangal Deep GUPTA1, Rajee Kuma CHAUHAN 1 1Depa men o Elec onics and Communica ion Enginee ing, Madan Mohan Mala iya Uni e si y o Technology, Deo ia Road, Go akhpu , 273016 U a P adesh, India 2Depa men o Elec onics and Communica ion Enginee ing, Ins i u e o Enginee ing & Technology, Deen Dayal Upadhyay Go akhpu Uni e si y, Go akhpu , 273009 U a P adesh, India p iy[email p o ec ed], na end ayada [email p o ec ed], [email p o ec ed], kc[email p o ec ed] DOI: 10.15598/aeee. 20i1.4258 A icle his o y: Recei ed Jun 10, 2021; Re ised Oc 17, 2021; Accep ed Oc 19, 2021; Published Ma 31, 2022. This is an open access a icle unde he BY-CC license. Abs ac . The choice o ga e me al echnology o junc ionless ansis o s needs o ha e di e se cha ac- e is ics as me als ha e dis inc wo k unc ions and hence, hey show incompa ibili y while ailo ing h esh- old o he de ice. In such a scena io, bime allic s acked ga e can be a p omising candida e o p esen wide ange o unable wo k unc ions equi ed o nano- egime junc ionless ansis o s. This pape explo es he elec onic phenomena occu ing a me al-me al in e - ace and he impac o Pla inum (P )/Ti anium (Ti) bime allic s acked ga e-based wo k unc ion unabil- i y on he RF and he mal pe o mances o p- ype window-based Silicon on Insula o Junc ionless T an- sis o (SOI JLT) using nume ical simula o SILVACO ATLAS. The pa ame e s conside ed o pe o mance e alua ion a e ON-s a e cu en (ION ), OFF-s a e cu - en (IOF F ), ION /IOF F a io, ansconduc ance (gm), cu o equency ( T), T ansconduc ance F equency P oduc (TFP), In insic Ga e Delay (IGD), in in- sic gain (AV), and Global De ice Tempe a u e (GDT). The gm, T, TFP, AVand GDT imp o e o modi- ied o e con en ional in he ON s a e a highe wo k unc ion, while IGD imp o es a lowe wo k unc ion. The imp o emen s o 11.7 % and 2.21 % a e ob ained in maximum gmand T, espec i ely, o modi ied an- sis o o e con en ional. The indings sugges ha bime allic s acked ga e modi ied SOIJLT is a be e op- ion han con en ional o low-powe RF applica ion. Keywo ds Bime allic s acked ga e, Junc ionless T ansis- o (JLT), Radio F equency (RF), Silicon-on- Insula o (SOI), he mal pe o mance and un- able wo k unc ion. 1. In oduc ion Minia u iza ion o MOS de ices aces majo challenges such as Sho Channel E ec s (SCEs) in he nanoscale egime [1]. Downscaling o in e sion mode FET de- ices has led o c ea ion o e ec s like ho ca ie e ec , D ain-Induced Ba ie Lowe ing (DIBL), poo sub h eshold swing, e c. inside he de ice due o which pe o mance has deg aded [1]. Ul a-shallow junc ion is one o he solu ions o SCEs in he in e sion mode de ices bu is e y complex and di icul om ab ica- ion cos and p ocess poin s o iew [2]. The e o e, in 2010, esea che s came up wi h a new de ice, popu- la ly known as “Junc ionless FET (JLFET)” o “ga ed esis o ”, as a plausible solu ion o in e sion mode de- ices [3]. I is hea ily doped semiconduc o de ice wi h sou ce, channel, and d ain and all h ee a e doped wi h he same uni o m doping ype and same concen a ion [3]. Hence, he e is no p-n junc ion exis ing inside he semiconduc o de ice. The ope a ion o his ga ed e- sis o shi s om olume deple ion (o channel egion in OFF s a e) in o pa ial deple ion and subsequen ly ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 73 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH in la band condi ion and accumula ion egion wi h he applica ion o ga e ol age [3]. Wo k unc ion is conside ed as one o he impo - an pa ame e s o he selec ion o ga e me al ma e- ial. The ga e elec ode wo k unc ion is u ilized as an e icien ool o u n o he JLFETs by accomplish- ing olume deple ion in he OFF s a e [4]. As he ac i e laye in JLFET is hea ily doped, he ull de- ple ion is achie ed in JLFET a VGS = 0 V. A ga e elec ode wi h a high wo k unc ion (>= 5.1eV) is e- qui ed o n-JLFETs, while one wi h low wo k unc ion (<= 4.1eV) is equi ed o p-JLFETs [4]. This is in di ec con as o he wo k unc ion equi emen s o con en ional FET de ices [5]. In e es ingly, a sui able ange o wo k unc ions (5.0 eV o 5.3 eV), also e med as wo k unc ion window, has been sugges ed o ob ain op imum pe o mance om junc ionless ansis o o low-powe applica ions in a nanoscale egime [6]. The e ec o single me als on RF pe o mance o junc ion- less ansis o s has al eady been p esen ed in [7]. The SOI JLTs (Silicon-on-Insula o Junc ionless T ansis o s) ha e he plana a chi ec u e compa i- ble wi h Complemen a y Me al Oxide Semiconduc o (CMOS) echnology, and hey ha e a single op ga e. The polysilicon ga es ha e been eplaced by he me al ga es due o he poly-deple ion e ec s and he pen- e a ion o dopan s h ough he ga e dielec ic laye [8]. The a ailable op ions o me als ha e di e en wo k unc ions which a e sui able o n- ype and p- ype JLTs [9]. The bene i o polySi ga e is ha i s e ec i e wo k unc ion (EWF o Φme ) could be modi ied depending on doping concen a ion, bu he pu es me als ha e inhe en alue, so hei EWF canno be modi ied [10]. I some me al has he equi ed alue o wo k unc ion needed o he desi ed h eshold ol age a ga e, hen he e a e p oblems wi h i s he mal s abili y and ad- hesi eness o dielec ic and semiconduc o ma e ials. To ailo he h eshold ol age o he de ice, a s ong app oach is ca ied ou when he ga e ma e ial should ha e a unable wo k unc ion [5]. The e o e, ga e me - als wi h unable wo k unc ion a e highly p e e able o CMOS in eg a ion [11]. Va ious ga e elec ode echnologies o achie e un- able wo k unc ion ha e been in es iga ed, such as me al silicides [12], me al ni ides [13], [14] and [15], bina y me al alloys [16], [17], [18] and [19] and bime al s acks [20], [21] and [22]. Among hese, bime allic s acked ga e has shown a wide ange o wo k unc- ion unabili y and ease o deposi ion [20]. This pape aims o explo e he elec onic phenom- ena aking place a me al-me al in e ace. Then, he impac o Pla inum (P )/Ti anium (Ti) bime allic s acked ga e-based wo k unc ion unabili y is s ud- ied on he RF and he mal pe o mance o p- ype window-based SOI JLT. The pa ame e s conside ed o pe o mance e alua ion a e ON cu en (ION ), OFF- s a e cu en (IOF F ), ansconduc ance (gm), cu o equency ( T), T ansconduc ance F equency P od- uc (TFP), In insic Ga e Delay (IGD), in insic gain (AV), and Global De ice Tempe a u e (GDT). The emaining pa o his pape is o ganized as ollows: Sec. 2. explains he elec onic phenomena ak- ing place a he me al-me al in e ace. The p oposed de ice s uc u e, i s p ocess low and i s simula ion me hodology a e discussed in Sec. 3. , Sec. 4. and Sec. 5. co espondingly. Sec ion 6. discusses he simula ion esul s o he p oposed JLT ansis o and compa es he pe o mance pa ame e s wi h con- en ional JLT. Sec ion 7. concludes he wo k. 2. Tunable Wo k Func ion Using Bime allic S acked Ga e In a bime allic s acked ga e, wo di e en me als a e g own o e he ga e dielec ic sequen ially in s acked manne , p o iding ha bo om me al ouching he di- elec ic should be much hinne han he op me al. He ein, he wo k unc ion can be uned o desi ed alue by a ying he bo om me al hickness, assuming ha op me al is hick enough [20]. The e ec i e wo k unc- ion alue anges be ween he wo k unc ions o wo me als used. The mo e accu a e explana ion o his wo k unc- ion unabili y is based on quan um size e ec s as he hickness o he bo om me al dec eases con inuously [20]. The wo isola ed dis inc me als possess he same acuum le el (E ac) bu hei espec i e Fe mi le els (EF1 o me al-1 and EF2 o me al-2) a e di e en o hem due o he a ying o wo k unc ion (Φm) om me al o me al [23], as shown in Fig. 1(a) [20]. I is assumed ha me al-1 has lowe wo k unc ion han me al-2 (Φm1<Φm2). Conside ing he sha p a omic p o iles and no in e - di usion be ween he wo me als, when wo me als a e in elec ical con ac wi h each o he , an in e ace is o med in in ima e con ac . By i ue o chemical equilib ium, he chemical po en ial should be cons an h oughou he in e ace, which means ha Fe mi le el o wo me als should be cons an a equilib ium nea he in e ace [24]. The e o e, elec ons will low om lowe wo k unc- ion o me al-1 o highe wo k unc ion o me al-2 and inc ease he densi y o s a es, un il Fe mi le el ge s aligned and becomes he same o bo h me als (Fig. 1(b)). As a esul , me al-1 is deple ed o elec ons and me al-2 has an excess o elec ons. The concluding space cha ge, posi i e in me al-1 and nega i e in me al- ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 74 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH 2, o ms an in e ace dipole laye composed o posi i e ion co es (me al-1) and displaced ee elec ons (me al- 2) [23]. The esul ing po en ial dis ibu ion (Φ(x)) and cha ge densi y (ρ(x)) is depic ed in Fig. 1(b). Φm2 Φm1 E ac EF2 EF1 Me al-1Me al-2 [Assump ion] 1) Φm1 < Φm2 2) The Me al-1 is much hinne han Me al-2 (bulk). Be o e con ac o ma ion (a) EF1 EF2 Φm1 Φme E ac E ac Φm2 Me al-2 Me al-1 ρ(x) E(x) φ(x) + - A e con ac o ma ion d’’m1 dm1 (b) Fig. 1: Band s uc u e o me al-me al in e ace (a) be o e con- ac o ma ion and (b) a e con ac o ma ion [20]. Due o dipole c ea ed, he e lies an elec ic ield (E(x)) which con i ms ha he acuum le el (E ac) becomes sloppy in na u e [24], as shown in Fig. 1(b). Because o ‘sc eening’ phenomena in me als, ee elec- ons nea cha ge in dipole dis ibu ion ge pola ized and edis ibu e o lowe he ene gy o he sys em. The dipole wid h emains limi ed o a ew Angs oms only. In he bulk egion, his e ec anishes no ab up ly bu con inuously. Hence, he posi ion o E ac also changes con inuously mo ing om in e ace o bulk and he sepa a ion o EF(Fe mi le el) and E ac) ( ac- uum le el) a ains cons an alue in he bulk o me al. F om Fig. 1(b), i is obse ed ha in he case o hick me al-1 ( hickness dm1), he elec on edis ibu ion p ocess (elec on ans e om me al-1 o me al-2) will cause less change in elec on densi y as compa ed o he bulk s a e in me al-1. Thus, in hick me al-1, junc ion dep h will be sho e and, a ga e dielec ic, alue o wo k unc ion Φm1will appea . In he case o e y hin me al-1 ( hickness d′′ m1), he elec on densi y will be d as ically educed. Consequen ly, his will inc ease junc ion dep h and a modi ied alue o wo k unc ion will appea on he ga e dielec ic (Φm1<Φme ) [20]. Some esea che s ha e p esen ed a model o band alignmen o he mul i-me al ga ed MOS s uc u e [8]. An analy ical model o he E ec i e Wo k Func ion (EWF) o a bime allic s acked ga e has been p oposed [25]. Acco ding o his, Φme =dm1 τΦm1+1− dm1 τΦm2,(1) whe e 0< dm1< τ. ‘τ’ is known as he ansi ion leng h nea he in e ace, which depends on he an- nealing condi ions, and is he leng h o e which he en- i e ange o unable wo k unc ion is ob ained, a ying om wo k unc ion o he i s me al o ha o he sec- ond me al. He e, Φme is he e ec i e wo k unc ion, Φm1is wo k unc ion o me al-1, Φm2is wo k unc- ion o me al-2 and dm1 is hickness o me al-1. This model conside s no in e mixing be ween he op me al and he ga e dielec ic and, hence, he bo om me al also se es as a ba ie laye be ween he wo. The analy ical a ia ion o bime allic s acked ga es such as Ti/Au and Ni/Au has been ound o be in consis en wi h expe imen al esul s [10]. The ela i e o de o me al laye s p o oundly a ec s he elec ical beha io o ansis o s. I elec ons a e dominan in he ga e s uc u e, hen he bo om me al ha ing a lowe Φmand op me al ha ing a highe Φm will make imp ope a angemen as du ing he edis- ibu ion p ocess bo om will become deple ed o elec- ons, which will ul ima ely p oduce ga e deple ion e - ec s, hus slowing down he swi ching speed o he ansis o . Bu i o de is e e sed ( op me al wi h low Φmand bo om me al wi h high Φm), elec ons will accumula e in bo om me al, hus inc easing he popula ion densi y, which successi ely dec eases ga e deple ion and inc eases he cu en d i e and speed o ansis o . The ga e s uc u e wi h dominan ca ie s as holes o ms p ope a angemen when bo om me al has low Φmwhile he op me al has high Φm[26]. The P /Ti bime allic s ack is used in his wo k be- cause i shows a wide EWF ange a ying om Ti (3.9 eV) o P (5.3 eV), nea ly ∼1.4eV and his ange is ob ained a e 300 ◦C FGA annealing wi h τ∼6nm [27]. Due o he conside a ion o n-channel JLT he e, P ha ing a highe Φmhas been placed a he bo om laye . 3. De ice S uc u e & Speci ica ion The c oss-sec ional iews o he p oposed bime al- lic s acked ga e-based con en ional SOI JLT (BSG_CSJLT) and modi ied SOI JLT (BSG_MSJLT) de ice s uc u es a e shown in Fig. 2(a) and Fig. 2(b) espec i ely. The BSG_MSJLT has a plana SOI s uc u e wi h sou ce, d ain, and channel doped wi h he same n- ype impu i y and concen a ion, hus elimina ing me allu gical junc ions like hose ha exis in con en ional SOI-MOSFET. In addi ion, a p- ype window is opened in he bu ied oxide laye and is in e ical alignmen wi h he chan- nel and ga e. The eason is ha i will help o achie e ull deple ion and educed OFF s a e leakage by educ- ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 75 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH ing he e ec i e channel hickness. The opened win- dow has leng h 22 nm, i.e. he same as ha o he channel. The s uc u al pa ame e s o designing he p- ype window-based modi ied SOI JLT a e abula ed in Tab. 1. I me i s e e encing ha s uc u al pa am- e e s o modi ied SOI JLT a e ca e ully coo dina ed ac- co ding o he desc ip ion in [28]. The p oposed modi- ica ion o he ga e elec ode is implemen ed by s ack- ing pla inum (bo om me al) and i anium ( op me al) o e ga e oxide. Ti anium (Ti) has a ixed hickness o 30 nm while pla inum (P ) hickness is kep a iable as i will help o une he desi ed wo k unc ion bu is kep below he ansi ion leng h (τ∼6nm) [27]. To analyze he impac on he pe o mance pa ame e s o he junc ionless de ices, he wo k unc ion ange con- side ed is om 5.0 o 5.3 eV. The speci ica ions o BSG_CSJLT a e he same as hose o BSG_MSJLT excep ha i does no ha e a p- ype pocke window. P-subs a e Bu ied Oxide N+ Ga e oxide D ainSou ce Ti anium (Ti) Pla�num (P ) N+ N+ Ga e (a) P-subs a e Bu ied Oxide N+ p- ype window Ga e oxide D ainSou ce Ti anium (Ti) Pla�num (P ) N+ N+ Ga e (b) Fig. 2: Two-dimensional s uc u es o (a) BSG_CSJLT and (b) BSG_MSJLT. 4. P ocess Flow The p ocess low o ab ica ing he BSG_MSJLT is included in Fig. 3. To ob ain he inal s uc u e o he p oposed de ice, sma -cu echnique [29] o gene a e a silicon ilm hickness o 10 nm is used and is ollowed by he s ages as ou lined. Low-dose Sepa a ion by Implan ed Oxygen (SIMOX me hod) can be used o p oduce oxide on bo h sides o he doped pocke [30] and [31]. As demons a ed in Fig. 3, oxygen ions can be implan ed wi h app op ia e doses and op imal implan ene gies (2.5−4.8·1017 O+ cm−2a op imized implan ene gies o 70 −140 KeV) [31] and [32]. The o ma ion o he ga e can be ca ied ou by sequen ially deposi ing he wo me als wi h di e en wo k unc ions o e ga e oxide using he E-beam e ap- o a ion me hod. La e , he ga e s ack is subjec ed o Fo ming Gas Anneal (FGA) a e he plasma ga e e ch [27]. The annealing empe a u e decides he ansi ion leng h o med a he con ac o wo me als, o e which a unable wo k unc ion ange is ob ained. N- ype silicon Bu ied Oxide Subs a e (a) n- ype doped op laye o SOI wa e . p- ype pocke implan N- ype silicon Oxide Bu ied Oxide Subs a e Ni ide (b) Oxida ion, Ni ida ion and e ching ga e o implan p- ype pocke . Bu ied Oxide N- ype silicon p- ype Pocke Subs a e Oxide (c) Oxide ealisa ion using low dosage SIMOX echnique. ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 76 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH Tab. 1: S uc u al pa ame e s conside ed o BSG_MSJLT de ice simula ion. S. no. Pa ame e name Symbol Pa ame e alue Uni 1Ga e leng h Lg22 nm 2Channel hickness si 10 nm 3Ga e oxide hickness (EOT) ox 1 nm 4Bu ied oxide hickness box 80 nm 5Ga e wo k unc ion Φm5, 5.1, 5.2 and 5.3 eV 6Opened window hickness Tow 25 nm 7Ac i e egion doping (n- ype) ND1·1019 cm−3 8Opened window doping (p- ype) Now 1·1013 cm−3 9Subs a e doping (p- ype) NA1·1018 cm−3 N- ype silicon Bu ied Oxide Subs a e (d) Top laye ga e oxida ion. Subs a e Bu ied Oxide N- ype silicon Me al-1 Me al-2 (e) Sequen ial deposi ion o wo dis inc ga e me als by E-beam e apo a ion ollowed by annealing. Bu ied Oxide N- ype silicon Subs a e Sou ce D ain Pocke ( ) Sou ce and D ain con ac o ma ion. Fig. 3: P oposed p ocess low o ab ica ing BSG_MSJLT. 5. Simula ion En i onmen and Me hodology The simula ion o de ice s uc u es and ex ac ion o a ious pa ame e s has been ca ied ou using he SIL- VACO ATLAS-2D de ice simula o . To ep esen ex- ac e-enac men , a ious physical models a ailable in ATLAS 2D de ice simula o , which a e essen ially de- si ed o deep submic on de ice simula ion, ha e been employed [35]. The e midi ac s a is ics is used due o hea y doping in he channel egion. The Ene gy Balance T anspo model is enabled using hc e in he model s a emen , which se s he solu ion o elec on and hole balance. In ene gy balance model: Pois- son’s equa ion, ca ie con inui y equa ions, and en- e gy balance equa ions o mobile ca ie s a e sol ed sel -consis en ly. The sel -hea ing equa ion is com- bined wi h he a o emen ioned equa ions o conside he hea gene a ion wi hin he de ice. Selbe he ’s impac ioniza ion model is se using an impac selb s a emen . The la . emp model is also ini ialized o accoun o solu ion o la ice ene gy balance equa ion. The equi ed he mal bounda y condi ion is included by de ining a he mal con ac a bo om o he de ice ixed a 300 K using he he mcon ac s a emen . Va i- ous o he physical models included a e bgn o conside bandgap na owing e ec s, bb .s d model o analyze he e ec s o band- o-band unneling, c o inco po- a e mobili y dependence on channel doping and bo h ans e se and longi udinal elec ic ields, s h o in- clude Shockley-Read- Hall ecombina ion o he ixed mino i y ca ie li e ime, and auge model o conside Auge ecombina ions. The nume ical me hod chosen is block new on o calib a e he de ice solu ions o gi en bias ol ages. To app o e he SILVACO ATLAS ool, he simula ion se up is calib a ed wi h simula ion esul s o [28] which a e al eady calib a ed wi h expe imen al esul s o [33]. 6. Resul s and Discussion The expe imen al and analy ical a ia ions o e ec- i e wo k unc ion (Φme ) wi h changing hickness (dm1) o bo om me al-1 pla inum (P ) a e plo ed in Fig. 4, conside ing he equi alen MOS capaci o s uc- u e (included in Fig. 4). He e, he ansi ion leng h (τ) is conside ed o be 6 nm, ob ained a 300 ◦C FGA (Fo ming Gas Anneal) condi ion [27]. I can be seen ha he e ec i e wo k unc ion anges om 3.9 eV (Ti only) o 5.3 eV (P only) o P hickness a ia ion 0< dm1<6nm [27]. Thus, a wide ange o un- able wo k unc ion (∼1.4eV) can be achie ed wi h he P /Ti bime allic s acked ga e. The pe cen age di - e ence be ween expe imen al and analy ical EWF is ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 77 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH ound o be a maximum o 6.68 %, which is e y sa is- ac o y (less han 10 %). 0 1 2 3 4 5 6 3,8 4,0 4,2 4,4 4,6 4,8 5,0 5,2 5,4 P only Ti only P /Ti [27] P /Ti analy ical P Thickness, dm1 (nm) E ec i e wo k unc ion, ϕme (eV) Ti P SiO2 Si Fig. 4: The expe imen al and analy ical a ia ion o e ec i e wo k unc ion (Φme ) wi h pla inum me al hickness (dm1). The ole o ga e me al wo k unc ion in ope a ing junc ionless de ices is e y c i ical. The de ice pe o - mance is al e ed by he ga e me al wo k unc ion, since he la band ol age a ies linea ly wi h wo k unc ion. No mally, JLT is an ON de ice, so he channel should be ully deple ed o s op conduc ion in he OFF s a e. Wi h inc easing ga e me al wo k unc ion, he h esh- old shi s owa ds posi i e alue in n-channel JLT. Figu e 5 shows he ans e cha ac e is ics (ID-VGS) o SOI JLTs plo ed on loga i hmic scale. The OFF s a e is assumed o be a VGS = 0 V and ON s a e a VGS =VDS = 1 V. The OFF-s a e cu en (IOF F ) dec eases wi h inc easing wo k unc ion because in- c eased Φm esul s in he educ ion o minimum po- en ial in he channel egion, hus p o iding be e su- pe ision in OFF s a e. This e ec i ely educes s a ic powe dissipa ion inside he de ice. As obse ed om Fig. 5, he BSG_MSJLT shows lowe leakage han he BSG_CSJLT, due o be e deple ion achie ed in chan- nel egion owing o educed channel hickness in he BSG_MSJLT. Table 2 clea ly depic s his leakage cu - en educ ion imp o emen o BSG_MSJLT a each wo k unc ion alue. The basic weakness o SOI JLT is ela i ely low ION /IOF F a io and can be co ec ed by g ading he d ain doping le el [34]. In he ON s a e, a educ ion in ON cu en (ION ) is obse ed a highe wo k unc ion alues as he p esence o elec ons in he channel is no eased a highe wo k unc ion. Imp o ed ION is ob ained in BSG_MSJLT (Fig. 5(b)) o e BSG_CSJLT (Fig. 5(a)) because o enhanced elec on mobili y due o mi iga ed la ice hea ing. Hence, he combined e ec o lowe IOF F and highe ION inc eases he ION /IOF F a io o BSG_MSJLT mo e han ha o BSG_CSJLT, as p e- sen ed in Table 2. Thus, he ela i e swi ching powe will always be g ea e han 1. The e ec o highe Φmis mo e p onounced in IOF F han in ION , hence, ION /IOF F a io also enhances a highe wo k unc ion. This imp o emen na u e is consis en wi h esul s o [2]. 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 2×10-4 4×10-4 6×10-4 8×10-4 10-3 1,2×10-3 1,4×10-3 ϕm VDS=1 V Ga e ol age, VGS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV D ain cu en , ID (A∙µm-1) (a) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 2×10-4 4×10-4 6×10-4 8×10-4 10-3 1,2×10-3 1,4×10-3 VDS=1 V Ga e ol age, VGS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV ϕm D ain cu en , ID (A∙µm-1) (b) Fig. 5: D ain Cu en (IDS ) a ia ion agains ga e ol age (VGS) on loga i hmic scale o (a) BSG_CSJLT and (b) BSG_MSJLT. Figu e 6 depic s ansconduc ance (gm) a ia ion agains ga e ol age (VGS) o di e en ga e me al wo k unc ions a a d ain ol age o 1 V. The ansconduc- ance (in Eq. (2)) beha io s a di e en wo k unc ions a e e y much simila o each o he . The only di e - ence is ha he ga e ol age a which maximum gm appea s shi s owa ds a posi i e ol age alue wi h inc easing wo k unc ion. This ga e ol age shi is ex- plained by he linea dependence o la band ol age on he wo k unc ion. F om Fig. 6, i is e iden ha in compa ison o BSG_CSJLT (Fig. 6(a)), an imp o e- men o 11.7 % is achie ed in he maximum gm o ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 78 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH BSG_MSJLT (Fig. 6(b)). This e ec o wo k unc ion on he maximum gmo bo h de ices is abula ed in Tab. 2. 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 0,3 0,4 0,5 0,6 0,7 ϕm VDS=1 V gm=∂ID/∂VGS T ansconduc ance, gm (mS) Ga e ol age, VGS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV (a) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 0,3 0,4 0,5 0,6 0,7 ϕm VDS=1 V gm=∂ID/∂VGS T ansconduc ance, gm (mS) Ga e ol age, VGS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV (b) Fig. 6: T ansconduc ance (gm) a ia ion agains ga e ol age (VGS) o (a) BSG_CSJLT and (b) BSG_MSJLT. gm=∂ID ∂VGS .(2) Figu e 7 shows ou pu cha ac e is ics (ID-VDS ) a di e en ga e wo k unc ions o bo h de ices. The ga e ol age is a ied om 0.5 V o 2 V wi h a s ep o 0.5 V. Highe wo k unc ion esul s in a dec eased ON-s a e cu en in he sa u a ion egion. A di e en ga e ol ages, he BSG_MSJLT (Fig. 7(b)) is d i - ing la ge amoun o cu en han he BSG_CSJLT (Fig. 7(a)). This pe o mance imp o emen is e- lec ed a each wo k unc ion alue, hus, making he BSG_MSJLT mo e sui able o d i ing a la ge amoun o cu en e en a smalle d ain ol age (VDS ) han he BSG_CSJLT. 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 0,0 2,0×10-4 4,0×10-4 6,0×10-4 8,0×10-4 1,0×10-3 1,2×10-3 1,4×10-3 1,6×10-3 ϕm VGS= 2 V, ΔVGS= -0.5 V D ain ol age, VDS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV D ain cu en , ID (A∙µm-1) (a) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 0,0 2,0×10-4 4,0×10-4 6,0×10-4 8,0×10-4 1,0×10-3 1,2×10-3 1,4×10-3 1,6×10-3 1,8×10-3 ϕm VGS= 2 V, ΔVGS= -0.5 V D ain ol age, VDS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV D ain cu en , ID (A∙µm-1) (b) Fig. 7: D ain cu en (IDS ) a ia ion agains d ain ol age (VDS) o (a) BSG_CSJLT and (b) BSG_MSJLT. Figu e 8 shows he plo s o ga e- o-sou ce capaci- ance (Cgs) and ga e- o-d ain capaci ance (Cgd) mea- su ed agains he ga e ol age a di e en wo k unc- ions. I is ob ained by pe o ming small signal analysis wi h VDS = 1 V and equency o 100 MHz, a e dc analysis. The capaci ances inc ease wi h inc ease in ga e ol age. No imp o emen was ob ained in he ca- paci ance alues wi h inc easing ga e me al wo k unc- ion, only he posi ion o occu ence has shi ed o- wa ds posi i e ga e ol age due o change in la band ol age. In compa ison, i is obse ed ha a each ga e wo k unc ion alue, Cgd is educed o BSG_MSJLT (Fig. 8(b)) o e ha o BSG_CSJLT (Fig. 8(a)), bu BSG_MSJLT shows inc eased Cgs o e BSG_CSJLT. This is only due o he addi ional capaci i e coupling e ec a ising be ween he ga e and sou ce e minal due o he p-n junc ion o med in he e ical di ec ion o he n- ype channel and p- ype window. ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 79 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 0,24 0,26 0,28 0,30 0,32 0,34 0,36 ϕm ϕm VDS=1 V 5.0 eV 5.1 eV 5.2 eV 5.3 eV Ga e ol age, VGS (V) Ga e-sou ce capaci ance, Cgs ( F/μm ) 0,05 0,10 0,15 0,20 0,25 0,30 Ga e-d ain capaci ance, Cgd ( F/μm ) (a) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 0,28 0,30 0,32 0,34 0,36 ϕm ϕm VDS=1 V 5.0 eV 5.1 eV 5.2 eV 5.3 eV Ga e ol age, VGS (V) Ga e-sou ce capaci ance, Cgs ( F/μm ) 0,05 0,10 0,15 0,20 0,25 Ga e-d ain capaci ance, Cgd ( F/μm ) (b) Fig. 8: Ga e- o-sou ce capaci ance (Cgs) and ga e- o-d ain ca- paci ance (Cgd) measu ed agains he ga e ol age (VGS) o (a) BSG_CSJLT and (b) BSG_MSJLT. Figu e 9 shows he e ec o di e en ga e wo k unc- ions on cu o equency o ansi ion equency ( T) o junc ionless ansis o s. I is he equency a which he de ice e lec s uni y gain. Hence, highe Tis al- ways desi able o sui o RF applica ion. Also, he po- si ion o plo has shi ed o mo e posi i e ga e ol age wi h inc easing wo k unc ion due o inc eased de ice h eshold. As illus a ed in Fig. 9(b), BSG_MSJLT shows a maximum To 279.51 GHz, which is app oxi- ma ely 2.21 % imp o emen o e he maximum To 273.45 GHz shown by BSG_CSJLT (see Fig. 9(a) and Tab. 2). The inc ease in Cgs was compensa ed by in- c eased gmand dec eased Cgd and BSG_MSJLT s ill manages o p oduce highe T. T=gm 2π(Cgs +Cgd).(3) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 75 100 125 150 175 200 225 250 275 ϕm VDS=1 V T = gm/(2π(Cgs+Cgd)) Cu o equency, T (GHz) Ga e ol age, VGS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV (a) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 100 125 150 175 200 225 250 275 ϕm VDS=1 V T = gm/(2π(Cgs+Cgd)) Cu o equency, T (GHz) Ga e ol age, VGS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV (b) Fig. 9: Cu o equency ( T) a ia ion agains ga e ol age (VGS) o (a) BSG_CSJLT and (b) BSG_MSJLT. Figu e 10 shows Global De ice Tempe a u e (GDT) o bo h de ices changing wi h d ain ol age, wi h a y- ing wo k unc ion. Global empe a u e o de ice in- c eases wi h inc easing d ain ol age as elec on mo e- men in he channel ises wi h VDS due o which mo e he mal hea is ans e ed om ca ie o he la ice. The GDT has dec eased conside ably wi h inc easing wo k unc ion alue. The highes ise in empe a u e in BSG_MSJLT (Fig. 10(b)) a VDS = 1.5V and a Φm= 5.0eV is s ill less han 500 K, while GDT ises up o 600 K in BSG_CSJLT (Fig. 10(a)). Thus, i is e iden ha BSG_MSJLT g ea ly educes he de ice he mal hea ing issue. This educ ion in empe a u e is a ained due o he inse ion o ligh ly doped p- ype window in BSG_MSJLT which acili a es dissipa ion o hea on inc easing d ain ol age. In Tab. 2, he p oposed de ice BSG_MSJLT shows ON/OFF a io be e han BSG_CSJLT wi h open window doping (Now = 1 ·1013 cm−3) bu i is no ap- ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 80 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 20 |NUMBER: 1 |2022 |MARCH Tab. 2: Pe o mance compa isons o BSG_CSJLT, BSG_MSJLT and R_DGJLFET [6] in wo k unc ion ange om 5.0 eV o 5.3 eV. S. No. Pa ame e s Wo k unc ion 5.0 eV 5.1 eV BSG_ CSJLT BSG_ MSJLT (Now = 1 ·1013 cm−3) BSG_ MSJLT (Now = 1 ·1020 cm−3) R_DG JLFET [6] BSG_ CSJLT BSG_ MSJLT (Now = 1 ·1013 cm−3) BSG_ MSJLT (Now = 1 ·1020 cm−3) R_DG JLFET [6] 1IOF F (mA) 0.472 0.453 8.41e−10 1.1e−90.416 0.404 1.5e−11 3e−11 2ION (mA) 1.098 1.152 0.387 1.09 1.046 1.087 0.221 0.859 3ION /IOF F 2.32 2.54 7.15e89.8e82.51 2.69 1.4e10 2.7e10 4gm(max) (mS) 0.666 0.744 1.83 ∼2.20.666 0.744 1.83 ∼2.2 5 T(max) (GHz) 273.45 279.51 751.03 - 273.45 279.51 751.03 - S. No. Pa ame e s Wo k unc ion 5.2 eV 5.3 eV BSG_ CSJLT BSG_ MSJLT (Now = 1 ·1013 cm−3) BSG_ MSJLT (Now = 1 ·1020 cm−3) R_DG JLFET [6] BSG_ CSJLT BSG_ MSJLT (Now = 1 ·1013 cm−3) BSG_ MSJLT (Now = 1 ·1020 cm−3) R_DG JLFET [6] 1IOF F (mA) 0.371 0.367 2.69e−11 8.9e−13 0.337 0.335 5.17e−12 2.9e−14 2ION (mA) 0.988 1.02 0.058 0.608 0.928 0.943 0.009 0.365 3ION /IOF F 2.66 2.77 2.1e96.7e11 2.75 2.81 4.6e91.2e13 4gm(max) (mS) 0.666 0.744 1.83 ∼2.20.666 0.744 1.83 ∼2.2 5 T(max) (GHz) 273.45 279.51 751.03 - 273.45 279.51 751.03 - p eciable due o e y low alue. Howe e , by inc easing he doping le el o open window o Now = 1·1013 cm−3 [36], he ON/OFF a io can be inc eased by mani olds e en g ea e han 106, hus, main aining he eliabili y o he de ice. Table 3 summa izes he RF and he mal pe - o mance compa ison be ween BSG_MSJLT and BSG_CSJLT. Va ious alues o analog/RF pa ame e s a e calcula ed o di e en wo k unc ions in he ON s a e (a VGS =VDS = 1 V) using small signal ac analysis a 100 MHz. 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 300 350 400 450 500 550 600 ϕm Global de ice empe u e (K) D ain ol age, VDS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV VGS=1 V (a) 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 300 350 400 450 500 ϕm VGS=1 V Global de ice empe a u e (K) D ain ol age, VDS (V) 5.0 eV 5.1 eV 5.2 eV 5.3 eV (b) Fig. 10: Global de ice empe a u e a ia ion agains d ain ol - age (VDS) o (a) BSG_CSJLT and (b) BSG_MSJLT. AV=gm gd,(4) TFP =gm IDS · T,(5) IGD =VDD ION ·Cgg.(6) The ansconduc ance (gm) alue is obse ed o in- c ease wi h inc easing wo k unc ion in he ON s a e o bo h de ices bu gmis always highe o BSG_MSJLT ©2022 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 81