Browsing by Author "Chang, Chia-Ta"

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30-GHz Low-Noise Performance of 100-nm-Gate-Recessed n-GaN/AlGaN/GaN HEMTs
(2010-02-01)
Chang, Chia-Ta
;
Hsu, Heng-Tung
;
Chang, Edward Yi
;
Kuo, Chien-I
;
Huang, Jui-Chien
We demonstrate a 100-nm-gate-recessed n-GaN/AlGaN/GaN high-electron mobility transistor (HEMT) with low-noise properties at 30 GHz. The recessed GaN HEMT exhibits a low ohmic-contact resistance of 0.28 Omega . mm and a low gate leakage current of 0.9 mu A/mm when biased at V(GS) = -3 V and V(DS) = 10 V. At the same bias point, a minimum noise figure of 1.6 dB at 30 GHz and an associated gain of 5 dB were achieved. To the best of our knowledge, this is the best noise performance reported at 30 GHz for gate-recessed AlGaN/GaN HEMTs.
460-nm InGaN-Based LEDs Grown on Fully Inclined Hemisphere-Shape-Patterned Sapphire Substrate With Submicrometer Spacing
(2009-10-01)
Chang, Chia-Ta
;
Hsiao, Shih-Kuang
;
Chang, Edward Yi
;
Hsiao, Yu-Lin
;
Huang, Jui-Chien
This letter investigates 460-nm InGaN-based light-emitting diodes (LEDs) grown on a hemisphere-shape-patterned sapphire substrate (HPSS) with submicrometer spacing. The full-width at half-maximum of the (102) plane rocking curves for GaN layer grown on a conventional sapphire substrate (CSS) and HPSS are 480 and 262 arcsec, respectively. Such improvement is due to the reduction of the pure edge threading dislocations. At the forward current of 20 mA, the light output power of the LEDs grown on CSS and HPSS were 4.05 and 5.86 mW, respectively. This improvement of 44% light-output power can be attributed to the improved quality of the material and the increase of the light extraction by the fully inclined facets of the HPSS.
An Al(2)O(3) AlGaAs/InGaAs Metal-Oxide-Semiconductor PHEMT SPDT Switch with Low Control Currents for Wireless Communication Applications
(2010-01-01)
Wu, Yun-Chi
;
Lin, Yueh-Chin
;
Chang, Edward Yi
;
Lee, C. T.
;
Kei, Chi-Chung
An AlGaAs/InGaAs metal-oxide-semiconductor pseudomorphic high electron mobility transistor (MOS-PHEMT) single- pole-double-throw (SPDT) switch using Al(2)O(3) high-k gate dielectric by atomic layer deposition is fabricated. The MOS-PHEMT exhibited a comparable dc performance and a much lower gate current compared to PHEMT. Radio-frequency (rf) test shows that the MOS-PHEMT switch has an insertion loss of less than 0.5 dB, an isolation larger than 30 dB, a return loss larger than 15 dB, and an input power for 1 dB compression of 31.4 dBm at 2.5 GHz. Overall, MOS-PHEMT monolithic microwave integrated circuits switches have comparable rf performance to PHEMT switches but with much lower dc power consumption. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3380967] All rights reserved.
An Al2O3 AlGaAs/InGaAs Metal-Oxide-Semiconductor PHEMT SPDT Switch with Low Control Currents for Wireless Communication Applications
(2010-01-01)
Wu, Yun-Chi
;
Lin, Yueh-Chin
;
Chang, Edward Yi
;
Lee, C. T.
;
Kei, Chi-Chung
An AlGaAs/InGaAs metal-oxide-semiconductor pseudomorphic high electron mobility transistor (MOS-PHEMT) single- pole-double-throw (SPDT) switch using Al2O3 high-k gate dielectric by atomic layer deposition is fabricated. The MOS-PHEMT exhibited a comparable dc performance and a much lower gate current compared to PHEMT. Radio-frequency (rf) test shows that the MOS-PHEMT switch has an insertion loss of less than 0.5 dB, an isolation larger than 30 dB, a return loss larger than 15 dB, and an input power for 1 dB compression of 31.4 dBm at 2.5 GHz. Overall, MOS-PHEMT monolithic microwave integrated circuits switches have comparable rf performance to PHEMT switches but with much lower dc power consumption. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3380967] All rights reserved.
Changes of Electrical Characteristics for AlGaN/GaN HEMTs Under Uniaxial Tensile Strain
(2009-03-01)
Chang, Chia-Ta
;
Hsiao, Shih-Kuang
;
Chang, Edward Yi
;
Lu, Chung-Yu
;
Huang, Jui-Chien
This letter investigates the characteristics of unpassivated AlGaN/GaN high-electron mobility transistors (HEMTs) under uniaxial tensile strain. Mechanical stress can produce additional charges that change the HEMT channel current. is phenomenon is dependent upon gate orientation and may be the result of the piezoelectric effect and changes in electron mobility due to the applied uniaxial stress. In addition, results show that tensile strain reduces the transient current, which is, likely due to the additional donorlike surface states created through the piezoelectric effect.
Enhancement of the Schottky barrier height using a nitrogen-rich tungsten nitride thin film for the schottky contacts on AlGaN/GaN heterostructures
(2008-05-01)
Lu, Chung-Yu
;
Chang, Edward Yi
;
Huang, Jui-Chien
;
Chang, Chia-Ta
;
Lin, Mei-Hsuan
Tungsten, stoichiometric W2N, and nitrogen-rich W2N films were used as Schottky contacts on AlGaN/GaN heterostructures. The nitrogen content in the film was controlled by varying the nitrogen-to-argon gas flow ratio during the reactive sputter deposition. The diode with the nitrogen-rich film exhibited a higher Schottky barrier height and the leakage current was comparable to that of the Ni/Au Schottky contact. Analysis suggested that this was due to the increase of the tungsten nitride work function as the result of higher nitrogen incorporation. Furthermore, after 600 degrees C thermal annealing, the diode was stable and showed no change in the leakage current.
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
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Hsu, Heng-Tung
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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.
Linearity Characteristics of Field-Plated AlGaN/GaN High Electron Mobility Transistors for Microwave Applications
(2010)
Huang, Jui-Chien
;
Hsu, Heng-Tung
;
Chang, Edward-Yi
;
Lu, Chung-Yu
;
Chang, Chia-Ta
A field-plated (FP) AlGaN/GaN high electron mobility transistor (HEMT) was fabricated. Investigations on the linearity characteristics were performed through two-tone and wide band code division multiple access (WCDMA) modulated excitations. The FP-HEMT exhibited an improved breakdown voltage of 160 V compared with that of the conventional HEMT. Additionally, a higher output power of 25.4 dBm with 43% power added efficiency at a 30 V drain bias at 2 GHz was achieved. When biased at 30 V and 15 mA/mm current density, the third-order intermodulation (IM3) level was measured to be -27.1 dBc (at P(1dB)) and the adjacent channel power rejection (ACPR) was -33.8 dBc (at P(1dB)) under WCDMA modulation at 2 GHz. Measurement results revealed that the field-plated structure improved the linearity performance over the conventional structure at high output power levels even beyond P(1dB). (C) 2010 The Japan Society of Applied Physics
Material growth and device characterization of AlGaN/GaN single-heterostructure and AlGaN/GaN/AlGaN double-heterostructure field effect transistors on Si substrates
(2014-05-01)
Hsiao, Yu-Lin
;
Chang, Chia-Ao
;
Chang, Edward Yi
;
Maa, Jer-Shen
;
Chang, Chia-Ta
An Al0.2Ga0.8N/GaN/Al0.1Ga0.9N double-heterostructure field effect transistor (DH-FET) structure was grown on a 150-mm-diameter Si substrate and the crystalline quality of the epitaxial material was found to be comparable to that of an Al0.2Ga0.8N/GaN single-heterostructure field effect transistor (SH-FET) structure. The fabricated DH-FET shows a lower buffer leakage current of 9.2 x 10(-5) mA/mm and an improved off-state breakdown voltage of higher than 200V, whereas the SH-FET shows a much higher buffer leakage current of 6.0 x 10(-3) mA/mm and a lower breakdown voltage of 130 V. These significant improvements show that the Al0.2Ga0.8N/GaN/Al0.1Ga0.9N DH-FET is an effective structure for high-power electronic applications. (C) 2014 The Japan Society of Applied Physics
Method for forming required pattern on semiconductor substrate by thermal reflow technique
(2010-06-24)
Chang, Yi Edward
;
Chang, Chia-Ta
;
Hsiao, Shih-Kuang
The invention is disclosed that pattern on semiconductor substrate is fabricated by thermal reflow technique. Also, the pattern on semiconductor substrate having different sub-micron spacings can be fabricated by using different time for the thermal reflow technique process.
Oxygen ion implantation isolation planar process for AlGaN/GaN HEMTs
(2007-06-01)
Shiu, Jin-Yu
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Huang, Jui-Chien
;
Desmaris, Vincent
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Chang, Chia-Ta
;
Lu, Chung-Yu
A multienergy oxygen ion implantation process was demonstrated to be compatible With the processing of high-power microwave AlGaN/GaN high electron mobility transistors (HEMTs). HEMTs that are isolated by this process exhibited gate-lag- and drain-lag-free operation; A maximum output power density of 5.3 W/mm at V-gs = -4 V and V-ds = 50 V and a maximum power added efficiency of 51.5% at V-gs = -4 V and V-ds = 30 V at 3 GHz were demonstrated on HEMTs without field plates on sapphire substrate. This isolation process results in planar HEMTs, circumventing potential problems with enhanced gate leakage due to the gate contacting the 2-D electron gas at the mesa sidewall.
RF Characteristics of AlGaN/GaN HEMTs under Different Temperatures
(2012-01-01)
Chiu, Yu-Sheng
;
Huang, Jui-Chien
;
Lin, Tai-Ming
;
Chou, Yu-Ting
;
Lu, Chung-Yu
We present the Rf characteristics of 0.7-mu m gate length n-GaN/AlGaN/GaN high-electron mobility transistors (HEMTs) with different source-drain spacing tested under different temperatures.. The 7-mu m source-drain spacing device demonstrated 800 mA/mm drain current density and 257 mS/mm tranceconductance, and the 5-mu m source-drain spacing device demonstrated 700 mA/mm drain current density and 260 mS/mm tranconductance. The 7-mu m source-drain spacing device was measured at room temperatures of 25 degrees C and -40 degrees C, the current gain (f(T)) were 18 GHz and 21GHz and the maximum oscillation (f(max)(U)) frequency were 63 GHz-and 87 GHz, respectively The f(T) was nearly linearly dependent on the temperature. As operating temperature increased from -40 degrees C to 50 degrees C, the f(T) dropped more dramatically for the 5-mu m SD spacing device than for the 7-mu m device. The f(max) characteristic of 5-mu m SD spacing device decreases more dramatically above 125 degrees C than the 7-mu m SD spacing device. This phenomenon might be due to stronger phonon scattering for shorter channel device at high temperatures.
Study of the inversion behaviors of Al(2)O(3)/In(x)Ga(1-x)As metal-oxide-semiconductor capacitors with different In contents
(2010-01-01)
Wu, Yun-Chi
;
Chang, Edward Yi
;
Lin, Yueh-Chin
;
Kei, Chi-Chung
;
Hudait, Mantu K.
In(x)Ga(1-x)As III-V compound semiconductor metal-oxide-semiconductor field-effect transistors have become a popular topic recently due to the higher drift velocity, and lower effective mass of the In(x)Ga(1-x)As materials. The impact of In content on the accumulation and inversion behaviors of the Al(2)O(3)/In(x)Ga(1-x)As capacitors is investigated in this study. For the various In(x)Ga(1-x)As materials studied, the Al(2)O(3)/InAs MOS system showed the strongest inversion phenomena due to the shorter response time of minority carrier of InAs compared to other In(x)Ga(1-x)As materials. Also, very low gate leakage current in the 10(-8) A/cm(2) range was observed for these capacitors. These results demonstrate that Al(2)O(3)/InAs MOS system with strong inversion phenomena and low leakage gate current is potential candidate for future high-performance low power logic MOSFET applications. (C) 2009 Elsevier Ltd. All rights reserved.
Study of the inversion behaviors of Al2O3/InxGa1-xAs metal-oxide-semiconductor capacitors with different In contents
(2010-01-01)
Wu, Yun-Chi
;
Chang, Edward Yi
;
Lin, Yueh-Chin
;
Kei, Chi-Chung
;
Hudait, Mantu K.
InxGa1-xAs III-V compound semiconductor metal-oxide-semiconductor field-effect transistors have become a popular topic recently due to the higher drift velocity, and lower effective mass of the InxGa1-xAs materials. The impact of In content on the accumulation and inversion behaviors of the Al2O3/InxGa1-xAs capacitors is investigated in this study. For the various InxGa1-xAs materials studied, the Al2O3/InAs MOS system showed the strongest inversion phenomena due to the shorter response time of minority carrier of InAs compared to other InxGa1-xAs materials. Also, very low gate leakage current in the 10(-8) A/cm(2) range was observed for these capacitors. These results demonstrate that Al2O3/InAs MOS system with strong inversion phenomena and low leakage gate current is potential candidate for future high-performance low power logic MOSFET applications. (C) 2009 Elsevier Ltd. All rights reserved.