Browsing by Author "Lee, Ting-Chi"

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Impacts of gate recess and passivation on AlGaN/GaN high electron mobility transistors
(2007-02-01)
Chan, Chih-Yuan
;
Lee, Ting-Chi
;
Hsu, Shawn S. H.
;
Chen, Leaf
;
Lin, Yu-Syuan
In this study, the impacts of gate recess and passivation on AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. The trap-related characteristics were studied in detail by several different measurements including dc current-voltage, cur-rent collapse, gate lag, and flicker noise characterizations. With a Cl-2/Ar-recessed gate, drain current collapse factors (Delta I-max) of similar to 37.5 and similar to 6.9% were observed before and after SiN passivation. The gate lag measurements showed that the lagging phenomena almost disappear with SiN passivation for both Cl-2- and Cl-2/Ar-recessed devices. However, the flicker noise measurements revealed distinct noise levels of devices with different processes even after passivation. As the gate voltage (VG) changed from 2 to -4V, the devices recessed by Cl-2 exhibited lower drain noise current densities (S-ID/I-D(2) ranging from 2.8 x 10(-14) to 1.7 x 10(-12) Hz(-1) at 1 kHz) than those etched by Cl-2/Ar mixture gas (S-ID/I-D(2) ranging from 6.3 x 10(-14) to 6.0 x 10(-12) Hz(-1) at 1 kHz), whereas the devices without the recess process showed the lowest noise levels (S-ID/I-D(2) ranging from 2.8 x 10(-15) to 1.3 x 10(-13) Hz(-1) at 1 kHz). It was found that S-ID/I-D(2) increased monotonically when V-G changed from 2 to -4V. A bias dependence of the 1/f(gamma) slope gamma was observed, and a relatively large variation in the range of similar to 1.1 to 1.6 was found for devices recessed by Cl-2/Ar mixture gas. The number fluctuation model was employed to explain the observed trends. The results also indicated that the surface traps play an important role in these devices.
InAs-based heterostructure field-effect transistor using AlAs0.16Sb0.84 double barriers
(2014-07-03)
Lin, Yue-Min
;
Lin, Kun-Ping
;
Lee, Ting-Chi
;
Li, Meng-Ying
;
Lee, Chien-Ping
An InAs-channel heterostructure field-effect transistor on GaAs substrates is presented. The conduction channel was formed by the InAs/AlAs0.16Sb0.84/AlSb quantum well. With the addition of the AlAs0.16Sb0.84 layer, holes that are generated by impact ionisation at high voltages are effectively confined in the InAs channel because of the large Delta Ev in this type-I heterostructure. By suppressing the hole injection into and accumulation in the buffer layer, the feedback through the back gate is eliminated and excellent output characteristics were obtained. The fabricated devices had a threshold voltage of about -0.6 V with a channel mobility of 18 100 cm(2)/V-s and a sheet carrier density of 1.2 x 10(12) cm(-2).
InAs-based heterostructure field-effect transistor using AlAs0.16Sb0.84 double barriers
(2014-07-03)
Lin, Yue-Min
;
Lin, Kun-Ping
;
Lee, Ting-Chi
;
Li, Meng-Ying
;
Lee, Chien-Ping
An InAs-channel heterostructure field-effect transistor on GaAs substrates is presented. The conduction channel was formed by the InAs/AlAs0.16Sb0.84/AlSb quantum well. With the addition of the AlAs0.16Sb0.84 layer, holes that are generated by impact ionisation at high voltages are effectively confined in the InAs channel because of the large Delta Ev in this type-I heterostructure. By suppressing the hole injection into and accumulation in the buffer layer, the feedback through the back gate is eliminated and excellent output characteristics were obtained. The fabricated devices had a threshold voltage of about -0.6 V with a channel mobility of 18 100 cm(2)/V-s and a sheet carrier density of 1.2 x 10(12) cm(-2).
Square-Gate AlGaN/GaN HEMTs With Improved Trap-Related Characteristics
(2009-12-01)
Lin, Yu-Syuan
;
Wu, Jia-Yi
;
Chan, Chih-Yuan
;
Hsu, Shawn S. H.
;
Huang, Chih-Fang
In this brief, the trap-related characteristics of high-breakdown AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. Compared with a conventional multifinger layout, the square-gate design presented reduced the current collapse from 19% to 6% and almost eliminated the gate lag. The flicker noise density and the gate leakage decreased from 1.16 x 10(-10) to 1.17 x 10(-11) 1/Hz (f = 100 Hz) and from 7.36 x 10(-5) to 1.80 x 10(-6) A/mm (V(GS) = -4 V and V(DS) = 100 V), respectively. The breakdown voltage was also improved from 350 to 650 V. With the channel area away from the defects generated by the mesa etching process, the square-gate AlGaN/GaN HEMTs demonstrated excellent performance with much less trapping effects.