Estudo do comportamento de transistores MISHEMT com diferentes dielétricos de porta
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22-05-27
Autores
Carmo, Genilson Julião do
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Universidade Estadual Paulista (Unesp)
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Este trabalho tem como objetivo o estudo do comportamento elétrico do transistor MISHEMT (Isolante/AlGaN/AlN/GaN) a partir dos parâmetros elétricos do mesmo. O comportamento do transistor foi estudado variando-se o tipo do material isolante de porta, as dimensões do dispositivo (comprimento da porta, distancias porta/fonte e porta/dreno, profundidade dos contatos de fonte e dreno) e temperaturas de funcionamento do dispositivo. Como isolantes de porta, foram utilizados os materiais Si3N4 de 2nm de espessura e Al2O3 com 10nm de espessura. Em uma primeira análise, variou-se o comprimento do canal do transistor de 200nm até 600nm. Os dispositivos foram analisados operando em temperaturas variando de 25ºC à 200ºC. Nas análises seguintes, o comportamento do transistor foi estudado variando-se as distâncias de porta/fonte (LGS) e porta/dreno (LGD) e a profundidade dos contatos de fonte e dreno. As curvas de transferência para o dispositivo com isolante de Al2O3 apresentaram histerese, enquanto a histerese pode ser negligenciada para o dispositivo com isolante de porta Si3N4. Quando analisada a tensão de limiar (VT), o transistor com isolante de porta Si3N4 apresenta valores menos negativos de VT, melhor comportamento aos efeitos de canal curto e melhores respostas ao DIBL (Drain Induced Barrier Lowering). No entanto, quando a análise de VT inclui os efeitos da variação da temperatura, enquanto o transistor de Al2O3 apresentou um comportamento convencional (redução de VT com o aumento da temperatura), um comportamento não esperado ocorreu para os transistores com Si3N4. Este comportamento anômalo deve-se a uma dupla condução que foi observada mais facilmente na curva da transcondutância. Essa dupla condução parece estar relacionada às diferentes componentes de corrente do dispositivo estudado. Essa dupla condução da curva de gm sugere que a corrente total do dispositivo parece ser influenciada pela condução MOS e pela condução 2DEG (Two-dimensional electron gas). Esses canais de condução de corrente acontecem nas interfaces das junções dos materiais. Apesar do transistor de Si3N4 apresentar maiores valores de corrente de fuga pela porta, o que parece estar relacionado com a espessura do isolante, o transistor Al2O3 apresenta um importante auto aquecimento do dispositivo, sendo inapropriado para aplicações analógicas. O potencial do transistor com isolante de Si3N4 para aplicações analógicas foi avaliado e o mesmo apresentou bom desempenho do ganho intrínseco de tensão e mesmo com a variação da temperatura o dispositivo apresentou uma boa estabilidade térmica. Dispositivos com profundidade de contatos alcançando o topo do material AlGaN apresentaram maior degradação de gm e IDS em comparação com os dispositivos com contatos alcançando o material AlN. Quanto menores as distâncias LGS e LGD, menor a degradação de IDS e gm. O comportamento de IDS e gm pode ser explicado pelas resistências séries associadas as configurações estudadas. As curvas das bandas de condução e concentração de elétrons sugerem três prováveis canais de condução associados ao dispositivo estudado.
This work aims to study the behavior of an (insulator/AlGaN/AlN/GaN) MISHEMT transistor based on its electrical parameters. The behavior of the transistor was studied by varying the gate insulator, device dimensions and device operating temperatures. Two materials were used as gate insulators, Si3N4 with a thickness of 2nm and Al2O3 with a thickness of 10nm. The channel length of the transistor was also varied from 200nm to 600nm. The devices were analyzed at operating temperatures ranging from 25ºC to 200ºC. In the following analyses, the transistor's behavior was studied by varying the gate/source (LGS) and gate/drain (LGD) distances and the source and drain contacts depth. The transfer curves of the devices with Al2O3 insulator material showed hysteresis, while the hysteresis can be neglected for the devices with Si3N4 gate insulator material. In the threshold voltage analysis (VT), the Si3N4 transistor shows less negative VT values, better response to short channel effects and better response to DIBL. However, when the VT analysis includes the effects of temperature variation, the Al2O3 transistor shows conventional behavior (VT reduction with increasing temperature), while Si3N4 transistors show anomalous behavior. This anomalous behavior is due to double conduction, which was more easily observed in the transconductance curve. This double conduction seems to be related to the different current components of the device studied. This double conduction in the gm curve indicates that the overall current of the device seems to be affected by the MOS conduction and the 2DEG conduction. These current conducting channels occur at the interfaces of the materials. Although the Si3N4 transistor exhibits higher leakage current values through the gate, which seems to be related to the insulator thickness, the Al2O3 transistor exhibits significant self-heating of the device, which is unsuitable for analog applications. The Si3N4 transistor was evaluated for analog applications and showed good intrinsic voltage gain performance and even under temperature variation, the thermal stability of the device was good. Devices with contact depth reaching the top of the AlGaN material showed higher gm and IDS degradation compared to devices with contacts reaching the AlN material. The smaller the LGS and LGD distances, the smaller the IDS and gm degradation. The IDS and gm behavior is, most likely, explained by the series resistance associated with the studied configurations. The conduction bands and electron concentration curves suggest three probable conduction channels associated with the studied device
This work aims to study the behavior of an (insulator/AlGaN/AlN/GaN) MISHEMT transistor based on its electrical parameters. The behavior of the transistor was studied by varying the gate insulator, device dimensions and device operating temperatures. Two materials were used as gate insulators, Si3N4 with a thickness of 2nm and Al2O3 with a thickness of 10nm. The channel length of the transistor was also varied from 200nm to 600nm. The devices were analyzed at operating temperatures ranging from 25ºC to 200ºC. In the following analyses, the transistor's behavior was studied by varying the gate/source (LGS) and gate/drain (LGD) distances and the source and drain contacts depth. The transfer curves of the devices with Al2O3 insulator material showed hysteresis, while the hysteresis can be neglected for the devices with Si3N4 gate insulator material. In the threshold voltage analysis (VT), the Si3N4 transistor shows less negative VT values, better response to short channel effects and better response to DIBL. However, when the VT analysis includes the effects of temperature variation, the Al2O3 transistor shows conventional behavior (VT reduction with increasing temperature), while Si3N4 transistors show anomalous behavior. This anomalous behavior is due to double conduction, which was more easily observed in the transconductance curve. This double conduction seems to be related to the different current components of the device studied. This double conduction in the gm curve indicates that the overall current of the device seems to be affected by the MOS conduction and the 2DEG conduction. These current conducting channels occur at the interfaces of the materials. Although the Si3N4 transistor exhibits higher leakage current values through the gate, which seems to be related to the insulator thickness, the Al2O3 transistor exhibits significant self-heating of the device, which is unsuitable for analog applications. The Si3N4 transistor was evaluated for analog applications and showed good intrinsic voltage gain performance and even under temperature variation, the thermal stability of the device was good. Devices with contact depth reaching the top of the AlGaN material showed higher gm and IDS degradation compared to devices with contacts reaching the AlN material. The smaller the LGS and LGD distances, the smaller the IDS and gm degradation. The IDS and gm behavior is, most likely, explained by the series resistance associated with the studied configurations. The conduction bands and electron concentration curves suggest three probable conduction channels associated with the studied device
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Transistores, Semicondutores, Microeletrônica, Engenharia elétrica