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Author: Jinshan Shi Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The development of future flexible electronics requires combining high electrical performance devices (i.e. millimeter and sub-millimeter wave electronic devices) with mechanical flexiblility and stability. However, a variety of existing technologies such as organic thin film transistors, amorphous silicon, and polycrystalline-silicon are limited by their poor transport properties. High electron mobility transistors (HEMTs) based on III-V materials have been used in the field of ultra-high frequency microwave applications for a long time. This work develops a feasible method for transferring conventional HEMTs onto the flexible substrate. By the means of adhesive bonding technique, 100nm-gate InAlAs/InGaAs HEMTs have been transferred onto polyimide film (Kapton) and electrically characterized in static and dynamic regime. Through the epitaxial layers optimization, finally, the fabricated devices are able to suppress Kink effect and provide high cut-off frequencies (ft=160GHz and fmax=290GHz) in unbent condition. These microwave characteristics are comparable to those obtained on 100nm-gate HEMTs on rigid substrate. Moreover, measured devices for various bending radius and bending directions show no obvious electrical degradation (lower than 15%).
Author: Jinshan Shi Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The development of future flexible electronics requires combining high electrical performance devices (i.e. millimeter and sub-millimeter wave electronic devices) with mechanical flexiblility and stability. However, a variety of existing technologies such as organic thin film transistors, amorphous silicon, and polycrystalline-silicon are limited by their poor transport properties. High electron mobility transistors (HEMTs) based on III-V materials have been used in the field of ultra-high frequency microwave applications for a long time. This work develops a feasible method for transferring conventional HEMTs onto the flexible substrate. By the means of adhesive bonding technique, 100nm-gate InAlAs/InGaAs HEMTs have been transferred onto polyimide film (Kapton) and electrically characterized in static and dynamic regime. Through the epitaxial layers optimization, finally, the fabricated devices are able to suppress Kink effect and provide high cut-off frequencies (ft=160GHz and fmax=290GHz) in unbent condition. These microwave characteristics are comparable to those obtained on 100nm-gate HEMTs on rigid substrate. Moreover, measured devices for various bending radius and bending directions show no obvious electrical degradation (lower than 15%).
Author: Dongmin Liu Publisher: ISBN: Category : Ionization Languages : en Pages : 173
Book Description
Abstract: InAlAs/InGaAs high electron mobility transistors (HEMTs) are among the best-performing semiconductor devices in terms of speed, noise, and high frequency gain. However, because of the small bandgap of the InGaAs channel, these devices suffer from strong impact ionization in the channel layer, which makes them not suitable for microwave power application. One effective approach to solve the problem is adding a larger band gap material under thin InGaAs to form a composite channel structure. In this type of HEMTs, under high electric field, electrons in the InGaAs can gain enough energy to transfer into the sub-channel thus exploit its advantageous properties such as a higher breakdown field and a higher saturation electron velocity. InAsP is an excellent candidate for the composite channel material. In this study, we use pseudomorphic InAsP layer beneath InGaAs main channel to form composite channel HEMTs on InP substrate to suppress the impact ionization and simultaneously achieve excellent device performance. The composite channel HEMT layer-structure was designed based on the simulation of band structure and electron concentration distribution by solving the by solving Poisson and Schrodinger equation self-consistently. 1-D theoretical simulation shows that electrons are mainly confined in the InGaAs main channel at equilibrium and begin to transfer to InAsP sub-channel under a high drain bias. The device structure was grown on InP substrate by molecular beam epitaxy by our collaborating research group. The composite channel devices are fabricated by a mesa-isolated HEMT process. The first fabricated 0.25 um gate length HEMTs exhibited a peak extrinsic transconductance of 888 mS/mm, an fT of 115 GHz, and an fmax of 137 GHz. A 0.15 um gate device showed an fT of 195 GHz. To our knowledge, these are the highest fTs reported for composite channel HEMTs on InP substrate with the same gate length. Furthermore, we present a systematic study on the gate length scaling of InGaAs/InAsP composite channel HEMTs. Devices with gate lengths of 0.15, 0.34, 0.58, 0.85 and 1.13 um were fabricated. The dependence of direct current and microwave performance on gate length is characterized. Device characterization results showed the extrinsic transconductance increased from 498 mS/mm for 1.13 um devices to 889 mS/mm for 0.15 um gate devices, while the unit current gain frequency increased from 24 GHz to 195 GHz. A simple delay time analysis is employed to extract the effective carrier velocity of the composite channel. Then we aim to improve its microwave performance by down scaling the gate length. High resolution electron beam lithography process using a ZEP/PMGI/ZEP resist stack for ultra-short T-gates was developed. A recent InGaAs/InAsP HEMTs composite channel with a gate-length of 80 nm exhibits a unity current gain cut-off frequency fT of 280 GHz. A 10 element small signal equivalent circuit model is developed for device parameter extraction. The values of circuit elements are used in an extended delay time analysis to investigate the effect of enhanced veff at short gate length. The average electron velocity under the gate is determined in the 80 nm device.
Author: Tarek Zaki Publisher: Springer ISBN: 3319188968 Category : Science Languages : en Pages : 232
Book Description
This work takes advantage of high-resolution silicon stencil masks to build air-stable complementary OTFTs using a low-temperature fabrication process. Plastic electronics based on organic thin-film transistors (OTFTs) pave the way for cheap, flexible and large-area products. Over the past few years, OTFTs have undergone remarkable advances in terms of reliability, performance and scale of integration. Many factors contribute to the allure of this technology; the masks exhibit excellent stiffness and stability, thus allowing OTFTs with submicrometer channel lengths and superb device uniformity to be patterned. Furthermore, the OTFTs employ an ultra-thin gate dielectric that provides a sufficiently high capacitance to enable the transistors to operate at voltages as low as 3 V. The critical challenges in this development are the subtle mechanisms that govern the properties of aggressively scaled OTFTs. These mechanisms, dictated by device physics, are well described and implemented into circuit-design tools to ensure adequate simulation accuracy.
Author: Wendi Zhou Publisher: ISBN: Category : Languages : en Pages :
Book Description
"Compound semiconductor gallium nitride high electron mobility transistors (HEMTs) have significant potential for use in the electronics industry, including radar applications and microwave transmitters for communications. These wide band gap semiconductors have unique material properties that lead to devices with high power, efficiency, and bandwidth compared with existing technologies. In this work, the electrical properties of gallium nitride HEMTs on silicon substrates were studied in the context of drain characteristics and breakdown voltage. The design, fabrication, and characterization of different devices are presented, in addition to a discussion on the effects of annealing and different gate contact materials. While demonstrating considerable promise in the field of high power radio frequency (RF) applications, this technology is yet immature and several fabrication issues still need to be addressed. The goal of this work is to represent a stepping stone in further developing this technology to be used in high power devices." --
Author: Jinshan Shi
Author: Jinshan Shi
Author: Dongmin Liu
Author: Hou Jang Lee
Author: 張玄昇
Author: 李博揚
Author: 高忠義
Author: Tarek Zaki
Author: William E. Winters
Author: Wendi Zhou
Author: Yi-Ching Pao