HTE Labs - 185 SPICE macro models for annular MOSFETs 186 Thermal distributions of surface states causing the current collapse in unpassivated AlGaN/GaN heterostructure field-effect transistors 187 Single-crystal organic field-effect transistors based on dibenzo-tetrathiafulvalene 188 High mobility transparent thin-film transistors with amorphous zinc tin oxide channel layer 189 Comment on "Carrier trapping and current collapse mechanism in GaN metal-semiconductor fieldeffect transistors" [Appl. Phys. Lett. 84, 1970 (2004)]

185 SPICE macro models for annular MOSFETs Author(s): K. Strohbehn, M.N. Martin (Affiliation: Appl. Phys. Lab., Johns Hopkins Univ., Laurel, MD, USA) Conference: 2004 IEEE Aerospace Conference Proceedings, Big Sky, MT, USA Conference Date: 6-13 March 2004 Sponsor(s): Aerosp. and Electron. Syst. Soc Publication: 2004 IEEE Aerospace Conference Proceedings (IEEE Cat. No.04TH8720) Publisher: IEEE, USA, 2004 Language: English ISBN: 0 7803 8155 6 Page: 2370-7 Vol.4 Document type: Conference paper Abstract: MOSFETs with annular, or enclosed, geometries arenow finding frequent use in rad-hard by design (RHBD)approaches to designing custom CMOS ASICs for aerospaceapplications. Unfortunately, these devices are not accuratelymodeled by the BSIM3 models normally provided for deviceswith ordinary rectangular gates. We present a SPICE macromodel for an annular n-channel MOSFET to account for theannular geometry effects on gate overlap capacitance andoutput conductance (5 refs.) Inspec No.: 8255595 186 Thermal distributions of surface states causing the current collapse in unpassivated AlGaN/GaN heterostructure field-effect transistors Author(s): C.S. Oh, C.J. Youn, G.M. Yang, K.Y. Lim, J.W. Yang (Affiliation: Dept. of Semicond. Sci., Chonbuk Nat. Univ., Chonju, South Korea) Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.12106-1-3 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: The dc characteristics of the AlGaN/GaNheterostructure field-effect transistors were examined attemperatures ranging from 25 to 260°C under white lightillumination. Drain current collapse measured was defined bythe difference of drain current between light on and light off atVgs=1 V and Vds=5 V. The surface-passivated device showedno drain current collapse, but the unpassivated device showedsevere drain current collapse at 25°C. Drain current and draincurrent collapse with an increase in temperature reduced,which resulted from the reduction of the electron mobility orsaturation velocity and the thermal activation of the trappedelectrons, respectively. Eventually, drain current collapsedisappeared completely above 250°C. The behavior of thetemperature-dependent drain current collapse showed that thesurface states for trapping electrons were continuouslydistributed with the temperature not having specific energystates (24 refs.) Inspec No.: 8247093 187 Single-crystal organic field-effect transistors based on dibenzo-tetrathiafulvalene Author(s): M. Mas-Torrent, P. Hadley (Affiliation: Kavli Inst. of NanoSci., Univ. of Technol., Delft, Netherlands), S.T. Bromley, N. Crivillers, J. Veciana, C. Rovira Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.12110-13 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: We report on the fabrication and characterization offield-effect transistors based on single crystals of the organicsemiconductor dibenzo-tetrathiafulvalene (DB-TTF). Wedemonstrate that it is possible to prepare very-good-qualityDB-TTF crystals from solution. These devices show high fieldeffectmobilities typically in the range 0.1-1 cm2/V s. Thetemperature dependence was also studied revealing an initialincrease of the mobility when lowering the temperature until itreached a maximum, after which the mobility decreasedfollowing a thermally activated behavior with activationenergies between 50 and 60 meV. Calculations of themolecular reorganization energy and intermolecular transferintegrals for this material were also performed and are inagreement with the high mobility observed in this material (25refs.) Inspec No.: 8247097 188 High mobility transparent thin-film transistors with amorphous zinc tin oxide channel layer Author(s): H.Q. Chiang, J.F. Wager (Affiliation: Sch. of Electr. Eng. & Comput. Sci., Oregon State Univ., Corvallis, OR, USA), R.L. Hoffman, J. Jeong, D.A. Keszler Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.13503-1-3 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: Transparent thin-film transistors (TTFTs) with anamorphous zinc tin oxide channel layer formed via rfmagnetron sputter deposition are demonstrated. Field-effectmobilities of 5-15 and 20-50 cm2 V -1 s-1 are obtained fordevices post-deposition annealed at 300 and 600°C,respectively. TTFTs processed at 300 and 600°C yielddevices with turn-on voltage of 0-15 and -5-5 V, respectively.Under both processing conditions, a drain current on-to-offratio greater than 107 is obtained. Zinc tin oxide is oneexample of a new class of high performance TTFT channelmaterials involving amorphous oxides composed of heavymetalcations with (n-1)d 10 ns0 (nges4) electronicconfigurations (25 refs.) Inspec No.: 8247132 189 Comment on "Carrier trapping and current collapse mechanism in GaN metal-semiconductor fieldeffect transistors" [Appl. Phys. Lett. 84, 1970 (2004)] Author(s): C.S. Oh, C.J. Youn, G.M. Yang, K.Y. Lim, J.W. Yang (Affiliation: Dept. of Semicond. Sci., Chonbuk Nat. Univ., Chonju, South Korea) Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.16101-1-2 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: In a recent Letter, Anwar et al. reported themechanism explaining the current collapse after theapplication of high drain bias and the current recovery at highdrain bias in the absence of illumination due to impactionization in the GaN metal semiconductor field-effecttransistors (MESFET). In previous reports, the currentcollapse was attributed to the hot electron effect at the GaNbuffer layer or the AlGaN barrier layer. In fact, both impactionization and the hot electron effect described equally thecurrent collapse as channel depletion due to channel electrontrapping. In their proposed model, electrons generated byimpact ionization are captured by neutral acceptor trap statesin the substrate located above the valence band. The chargedtrap states move to an energy level located near midgap,creating a positively charged depletion region in the channel,and causing current collapse. With increasing drain bias, thequasi-Fermi level approaches the charged trap states at thedrain end of the gate, initiating detrapping of the electrons andrestoring the current. In this Comment, it is argued that currentcollapse and current recovery at high drain bias cannot beeffectively explained by the impact ionization (3 refs.) Inspec No.: 8247145

	Semiconductor Devices - Miscellaneous articles, abstracts, technical notes, letters, publications
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185 SPICE macro models for annular MOSFETs Author(s): K. Strohbehn, M.N. Martin (Affiliation: Appl. Phys. Lab., Johns Hopkins Univ., Laurel, MD, USA) Conference: 2004 IEEE Aerospace Conference Proceedings, Big Sky, MT, USA Conference Date: 6-13 March 2004 Sponsor(s): Aerosp. and Electron. Syst. Soc Publication: 2004 IEEE Aerospace Conference Proceedings (IEEE Cat. No.04TH8720) Publisher: IEEE, USA, 2004 Language: English ISBN: 0 7803 8155 6 Page: 2370-7 Vol.4 Document type: Conference paper Abstract: MOSFETs with annular, or enclosed, geometries arenow finding frequent use in rad-hard by design (RHBD)approaches to designing custom CMOS ASICs for aerospaceapplications. Unfortunately, these devices are not accuratelymodeled by the BSIM3 models normally provided for deviceswith ordinary rectangular gates. We present a SPICE macromodel for an annular n-channel MOSFET to account for theannular geometry effects on gate overlap capacitance andoutput conductance (5 refs.) Inspec No.: 8255595	186 Thermal distributions of surface states causing the current collapse in unpassivated AlGaN/GaN heterostructure field-effect transistors Author(s): C.S. Oh, C.J. Youn, G.M. Yang, K.Y. Lim, J.W. Yang (Affiliation: Dept. of Semicond. Sci., Chonbuk Nat. Univ., Chonju, South Korea) Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.12106-1-3 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: The dc characteristics of the AlGaN/GaNheterostructure field-effect transistors were examined attemperatures ranging from 25 to 260°C under white lightillumination. Drain current collapse measured was defined bythe difference of drain current between light on and light off atVgs=1 V and Vds=5 V. The surface-passivated device showedno drain current collapse, but the unpassivated device showedsevere drain current collapse at 25°C. Drain current and draincurrent collapse with an increase in temperature reduced,which resulted from the reduction of the electron mobility orsaturation velocity and the thermal activation of the trappedelectrons, respectively. Eventually, drain current collapsedisappeared completely above 250°C. The behavior of thetemperature-dependent drain current collapse showed that thesurface states for trapping electrons were continuouslydistributed with the temperature not having specific energystates (24 refs.) Inspec No.: 8247093
187 Single-crystal organic field-effect transistors based on dibenzo-tetrathiafulvalene Author(s): M. Mas-Torrent, P. Hadley (Affiliation: Kavli Inst. of NanoSci., Univ. of Technol., Delft, Netherlands), S.T. Bromley, N. Crivillers, J. Veciana, C. Rovira Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.12110-13 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: We report on the fabrication and characterization offield-effect transistors based on single crystals of the organicsemiconductor dibenzo-tetrathiafulvalene (DB-TTF). Wedemonstrate that it is possible to prepare very-good-qualityDB-TTF crystals from solution. These devices show high fieldeffectmobilities typically in the range 0.1-1 cm2/V s. Thetemperature dependence was also studied revealing an initialincrease of the mobility when lowering the temperature until itreached a maximum, after which the mobility decreasedfollowing a thermally activated behavior with activationenergies between 50 and 60 meV. Calculations of themolecular reorganization energy and intermolecular transferintegrals for this material were also performed and are inagreement with the high mobility observed in this material (25refs.) Inspec No.: 8247097	188 High mobility transparent thin-film transistors with amorphous zinc tin oxide channel layer Author(s): H.Q. Chiang, J.F. Wager (Affiliation: Sch. of Electr. Eng. & Comput. Sci., Oregon State Univ., Corvallis, OR, USA), R.L. Hoffman, J. Jeong, D.A. Keszler Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.13503-1-3 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: Transparent thin-film transistors (TTFTs) with anamorphous zinc tin oxide channel layer formed via rfmagnetron sputter deposition are demonstrated. Field-effectmobilities of 5-15 and 20-50 cm2 V -1 s-1 are obtained fordevices post-deposition annealed at 300 and 600°C,respectively. TTFTs processed at 300 and 600°C yielddevices with turn-on voltage of 0-15 and -5-5 V, respectively.Under both processing conditions, a drain current on-to-offratio greater than 107 is obtained. Zinc tin oxide is oneexample of a new class of high performance TTFT channelmaterials involving amorphous oxides composed of heavymetalcations with (n-1)d 10 ns0 (nges4) electronicconfigurations (25 refs.) Inspec No.: 8247132
189 Comment on "Carrier trapping and current collapse mechanism in GaN metal-semiconductor fieldeffect transistors" [Appl. Phys. Lett. 84, 1970 (2004)] Author(s): C.S. Oh, C.J. Youn, G.M. Yang, K.Y. Lim, J.W. Yang (Affiliation: Dept. of Semicond. Sci., Chonbuk Nat. Univ., Chonju, South Korea) Journal: Appl. Phys. Lett. (USA), vol.86, no.1, p.16101-1-2 (3 Jan. 2005) Publisher: AIP, USA Language: English ISSN: 0003-6951, Full text Document type: Journal article Abstract: In a recent Letter, Anwar et al. reported themechanism explaining the current collapse after theapplication of high drain bias and the current recovery at highdrain bias in the absence of illumination due to impactionization in the GaN metal semiconductor field-effecttransistors (MESFET). In previous reports, the currentcollapse was attributed to the hot electron effect at the GaNbuffer layer or the AlGaN barrier layer. In fact, both impactionization and the hot electron effect described equally thecurrent collapse as channel depletion due to channel electrontrapping. In their proposed model, electrons generated byimpact ionization are captured by neutral acceptor trap statesin the substrate located above the valence band. The chargedtrap states move to an energy level located near midgap,creating a positively charged depletion region in the channel,and causing current collapse. With increasing drain bias, thequasi-Fermi level approaches the charged trap states at thedrain end of the gate, initiating detrapping of the electrons andrestoring the current. In this Comment, it is argued that currentcollapse and current recovery at high drain bias cannot beeffectively explained by the impact ionization (3 refs.) Inspec No.: 8247145

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