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Study of Charge Trapping Effects on AlGaN/GaN HEMTs Under UV Illumination With Pulsed I-V Measurement
(2020-06-01)
Nagarajan, Venkatesan
;
Chen, Kun-Ming
;
Chen, Bo-Yuan
;
Huang, Guo-Wei
;
Chuang, Chia-Wei
The charge trapping effects on AlGaN/GaN HEMTs under UV illumination are investigated using the pulsed current-voltage (I-V) measurement method. The test samples are unpassivated Schottky-gate HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) with SiN gate dielectric. For HEMTs, the dominant charge trapping sources are the surface trap states, whereas, for MIS-HEMTs, they are trap states in the SiN gate dielectric and GaN buffer. When these devices are shined with the UV light, the drain current increases apparently in both samples owing to the generated photocurrent. By combining the UV illumination and pulsed I-V measurement, we find out the UV light has less effect on the surface charge trapping in the unpassivated HEMTs. Moreover, in MIS-HEMTs, we observe the charge trapping in the SiN gate dielectric becomes more serious under UV illumination, whereas the charge trapping in the GaN buffer is suppressed significantly. These findings are important for designing a GaN-based HEMT for photonic applications. In addition, the different responses of the surface-, buffer-, and gate-dielectric-related charge trapping to the UV light suggest that it would be easier to distinguish the trap types by introducing the UV illumination during the pulse measurement.
Low-Frequency Noise Characterization of AlGaN & x002F;GaN HEMTs and MIS-HEMTs Under UV Illumination
(2020-01-01)
Nagarajan, Venkatesan
;
Chen, Kun-Ming
;
Lin, Hsin-Yi
;
Hu, Hsin-Hui
;
Huang, Guo-Wei
The low-frequency noise characteristics of AlGaN & x002F;GaN HEMTs and MIS-HEMTs are investigated in the dark condition and under UV illumination. The test devices with a 3-& x03BC;m-thick GaN buffer and a 25-nm-thick Al_0.22Ga_0.78N barrier layer were fabricated on the silicon wafer. For MIS-HEMTs, a 25-nm-thick SiN layer was deposited as a gate dielectric. The measured low-frequency noises show a 1 & x002F;f spectrum and can be described by the carrier number fluctuation model. Different noise responses to the UV light between HEMTs and MIS-HEMTs were observed. By comparing the noise data in dark and under UV illumination, the noise sources under the gate and in the ungated gate-drain access region have been identified. From these results, we can find a design guideline to improve the noise and reliability of GaN-based devices for optoelectronic applications.
An 80 nm In0.7Ga0.3As MHEMT with Flip-Chip Packaging for W-Band Low Noise Applications
(2010-01-01)
Wang, Chin-Te
;
Kuo, Chien-, I
;
Lim, Wee-Chin
;
Hsu, Li-Han
;
Hsu, Heng-Tung
The fabrication process of an 80 nm In0.7Ga0.3As MHEMT device with flip-chip packaging on Al2O3 substrate is presented. The flip-chip packaged device exhibited good dc characteristics with high I-DS = 425 mA/mm and high g(m) = 970 mS/mm at V-DS = 1.5 V. Besides, the RF performances revealed high gain of 10 dB at 50 GHz and low minimum noise figure (NFmin)below 2 dB at 60 GHz, showing the feasibility of flip-chip packaged In0.7Ga0.3As MHEMT device for low noise applications at W-band.
The effects of Growth Parameters on the Electrical Properties in InAlN/AlN/GaN High-Electron-Mobility Transistors (HEMTs)
(2014-01-01)
Huang, Wei-Ching
;
Wong, Yuen-Yee
;
Liu, Kuan-Shin
;
Hsieh, Chi-Feng
;
Chang, Edward Yi
The electrical properties in the InAlN/AlN/GaN high electron mobility transistor grown by metal-organic vapor deposition (MOCVD) with different growth parameters were investigated in this study. We observed that two-dimensional electron gas (2DEG) channel was influenced by thickness of AlN spacer layer and a stable stage prior to the growth of AlN spacer layer. The TEM images showed the generation of dislocations at interface between AlN/GaN and InAlN/AlN with the thicker AlN spacer layer. These dislocations acted as electron scattering center and degraded the electron mobility in the 2DEG channel. Besides, a too long stable stage also appeared degradation in the electron mobility due to the etching effect of H-2 gas. By optimizing growth parameters, the highest electron mobility of 890 cm(2)/V.s
Fabrication of AlGaN/GaN High Electron Mobility Transistors (HEMTs) on Silicon Substrate with Slant Field Plates Using Deep-UV Lithography Featuring 5W/mm Power Density at X-band
(2012)
Chang, Chia-Hua
;
Hsu, Heng-Tung
;
Huang, Lu-Che
;
Chiang, Che-Yang
;
Chang, Edward Yi
In this work, AlGaN/GaN HEMTs on silicon with slant field platehave been successfully fabricated using deep-UV lithography. By using an angle exposure technique, submicron T-shaped gates with slant sidewalls were achieved. The 0.6 x 100 mu m(2) slant-field-plated AlGaN/GaN HEMT on silicon substrate exhibited a peak value of transconductance of 214 mS/mm and a breakdown voltage of 122 V. Through high-frequency measurements, the device revealed a current gain cutoff frequency (f(T)) of 24 GHz, a maximum oscillation frequency (f(max)) of 49 GHz and an output power density of 5.0 W/mm at X-band.
A 40-nm-Gate InAs/In(0.7)Ga(0.3)As Composite-Channel HEMT with 2200 mS/mm and 500-GHz f(T)
(2009)
Kuo, Chien-I
;
Hsu, Heng-Tung
;
Wu, Chien-Ying
;
Chang, Edward Yi
;
Miyamoto, Yasuyuki
A 40-nm T-gate high-electron-mobility-transistor with InAs/In(0.7)Ga(0.3)As composite-channel has been fabricated. The device exhibits a transconductance (g.) of 2200 mS/mm, a cutoff frequency f(T) of 506 GHz and a minimum noise figure of 1.21 dB at a frequency of 58 GHz. These performances make the device well-suited for millimeter-wave or sub-millimeter-wave applications.
Investigation of Impact Ionization from In(x)Ga(1-x)As to InAs Channel HEMTs for High Speed and Low Power Applications
(2008)
Kuo, Chien-I
;
Hsu, Heng-Tung
;
Chang, Edward Yi
;
Chang, Chia-Ta
;
Chang, Chia-Yuan
80-nm high electron mobility transistors (HEMTs) with different Indium content in In(x)Ga(1-x)As channel from 52%, 70% to 100% have been fabricated. Device performances degradation were observed on the DC measurement and RF characteristics caused by impact ionization at different drain bias, >0.8V (InAs/In(0.7)Ga(0.3)As), > 1V (In(0.7)Ga(0.3)As) and > 1.5V (In(0.52)Ga(0.48)As), respectively. The impact ionization phenomenon should be avoided for high speed, low power application because it limits the highest drain bias of the device which in turn limits the drift velocity under specific applied electric field.

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