The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

Electronics based on two-dimensional materials

The rapid development of the RF power electronics requires the introduction of wide bandgap material due to its potential in high output power density, high operation voltage and high input impedance GaN-based RF power devices have made substantial progresses in the last decade This paper attempts to review the latest developments of the GaN HEMT technologies, including material growth, processing technologies, device epitaxial structures and MMIC designs, to achieve the state-of-the-art microwave and millimeter-wave performance The reliability and manufacturing challenges are also discussed

GaN-Based RF Power Devices and Amplifiers

Recent changes in how people consume multimedia services are causing an explosive increase in mobile traffic. With more and more people using wireless networks, the demand for the ultra-fast wireless communications systems is increasing. To date, this demand has been accommodated with advanced modulation schemes and signal-processing technologies at microwave frequencies. However, without increasing the carrier frequencies for more spectral resources, it may be quite difficult to keep up with the needs of users. Although there are several alternative bands, recent advances in terahertz-wave (THz-wave) technologies have attracted attention due to the huge bandwidth of THz waves and its potential for use in wireless communications. The frequency band of 275 ~ 3000 GHz , which has not been allocated for specific uses yet, is especially of interest for future wireless systems with data rates of 10 Gb/s or higher. Although THz communications is still in a very early stage of development, there have been lots of reports that show its potential. In this review, we will examine the current progress of THz-wave technologies related to communications applications and discuss some issues that need to be considered for the future of THz communications.

Present and Future of Terahertz Communications

Microwave photonics with superconducting quantum circuits

As silicon-based electronics approach the limit of improvements to performance and capacity through dimensional scaling, attention in the semiconductor field has turned to graphene, a single layer of carbon atoms arranged in a honeycomb lattice. Its high mobility of charge carriers (electrons and holes) could lead to its use in the next generation of high-performance devices. Graphene is unlikely to replace silicon completely, however, because of the poor on/off current ratio resulting from its zero bandgap. But it could be used to improve silicon-based devices, in particular in high-speed electronics and optical modulators.

A role for graphene in silicon-based semiconductor devices

PROBLEM TO BE SOLVED: To provide a method for forming a large-surface, high-gate-current HEMT diode by using a citric acid etchant. SOLUTION: The method for manufacturing an HEMT IC using a citric acid etchant, wherein a citric acid etchant including potassium citrate, citric acid and hydrogen peroxide is used to form gates of different sizes in a single etching step. A wafer is first spin-coated with photoresist and then the photoresist is subjected to an optical lithographic operation to be formed as a pattern. The wafer is immersed into the etchant to etch exposed semiconductor material. An metallic electrode is deposited on the wafer and photoresist remaining thereon is removed with solvent. COPYRIGHT: (C)2002,JPO

Method of forming large-area, high-gate-current hemt diode

Presented is a 3 watt Q-band PHEMT MMIC power amplifier module with a peak efficiency of 25% at 44.5 GHz, believed to be the highest reported at this power level and frequency. The waveguide power amplifier module features the use of thinned 2-mil GaAs MMICs with off-chip output matching and combining on a 5-mil alumina substrate.

3-watt Q-band waveguide PHEMT MMIC power amplifier module

In this paper, we present three MMIC low noise amplifiers using dual-gate GaAs HEMT devices in a balanced amplifier configuration. The designs target three different frequency bands including 5-9 GHz, 9-18 GHz and 20-40 GHz. These dual-gate balanced designs demonstrate the excellent qualities of balanced amplifiers in terms of bandwidth, matched characteristics and bandwidth, but demonstrate higher bandwidth than designs with a single-stage common-source device. Additionally, noise performance is excellent, with the 5-9 GHz LNA demonstrating <1.75-dB NF, the 9-18 GHz LNA < 2.75-dB NF and the 20-40 GHz LNA <2.5 dB NF. Demonstrating high gain and excellent bandwidth, the dual-gate devices seem a logical choice for the balanced amplifier topology.

Broadband Dual-Gate Balanced Low Noise Amplifiers

Low frequency noise technique was introduced to characterize the gate and drain noise spectra on 0.1 /spl mu/m InP HEMTs before and after degradation (subjected to elevated temperature lifetest at T/sub junction/ of 240 /spl deg/C for 936 hours). It has been found that the gate current noise on the degraded devices increases significantly and exhibits a Lorentzian peak around 15 KHz. The low frequency noise results indicate that the Schottky junction is the primary degradation origin, which is consistent with the electrical results - showing the forward and reverse Schottky junction degradation. Gate current low frequency noise spectra suggest that there are possible interface states and bulk defects generated in the degraded Schottky junction - this was further substantiated with a scanning transmission electron microscope. The results from this study shows that low frequency noise characterization provides a sensitive means to identify the degradation origin and Schottky junction attributes of a degraded InP HEMT.

http://ieeexplore.ieee.org/iel5/9837/30998/01442801.pdf

Degradation analysis of 0.1 /spl mu/m InP HEMTs using low frequency noise characterization

Apparatuses ( 10, 100 ), and methods of using same, for the simultaneous thinning of the backside surfaces of a plurality of semiconductor wafers (W) using a non-crystallographic and uniform etching process, are described. The apparatuses ( 10, 100 ) include a fixture ( 12, 102 ) having a plurality of horizontal receptacles ( 14, 16, 18, 20, 104, 106, 108, 110 ) for receiving the semiconductor wafers (W). The loaded fixtures ( 12, 102 ) are then immersed into an etchant solution ( 36, 146 ) that is capable of isotropically removing a layer of semiconductor material from the backside surface of the semiconductor wafers (W). The etchant solution ( 36, 146 ) is preferably heated to about 40° C.-50° C. and constantly stirred with a magnetic stirring bar ( 48, 158 ). Once a sufficient period of time has elapsed, the thinned semiconductor wafers (W) are removed from the etchant solution ( 36, 146 ). The apparatuses ( 10, 100 ) are capable of simultaneously thinning several semiconductor wafers (V) down to a final thickness of about 25 μm.

Richard Lai

Papers

Method of forming large-area, high-gate-current hemt diode

3-watt Q-band waveguide PHEMT MMIC power amplifier module

Broadband Dual-Gate Balanced Low Noise Amplifiers

Degradation analysis of 0.1 /spl mu/m InP HEMTs using low frequency noise characterization

Wafer thinning techniques