Method for noncontact measurement of 2DEG mobility and carrier density in AlGaN/GaN on semi-insulating wafers

We present a charge-assisted sheet resistance technique for noncontact wafer level determination of 2DEG mobility vs. sheet carrier density without any test structures or gates. Instead, the electrical biasing of 2DEG is provided by surface charge deposition, using a corona charging method. Analysis of the sheet resistance vs. deposited charge identifies the 2DEG full depletion condition and enables calculation of the 2DEG sheet carrier density required for the mobility. Results for AlGaN/GaN heterostructures on semi-insulating SiC and sapphire substrates show good agreement with Hall results at a zero-bias condition.

Circuit Optimization Method to Reduce Disturbances in Poly-Si 1T-DRAM

A capacitorless one-transistor dynamic random-access memory device (1T-DRAM) is proposed to resolve the scaling problem in conventional one-transistor one-capacitor random-access memory (1T-1C-DRAM). Most studies on 1T-DRAM focus on device-level operation to replace 1T-1C-DRAM. To utilize 1T-DRAM as a memory device, we must understand its circuit-level operation, in addition to its device-level operation. Therefore, we studied the memory performance depending on device location in an array circuit and the circuit configuration by using the 1T-DRAM structure reported in the literature. The simulation results show various disturbances and their effects on memory performance. These disturbances occurred because the voltages applied to each device during circuit operation are different. We analyzed the voltage that should be applied to each voltage line in the circuit to minimize device disturbance and determine the optimized bias condition and circuit structure to achieve a large sensing margin and realize operation as a memory device. The results indicate that the memory performance improves when the circuit has a source line and the bias conditions of the devices differ depending on the write data at the selected device cell. Therefore, the sensing margin of the 1T-DRAM used herein can expectedly be improved by applying the proposed source line (SL) structure.

Design and Analysis of a Frequency Reconfigurable Penta-Band Antenna for WLAN and 5G Applications

This paper presents a discussion on a low-profile, frequency-reconfigurable penta-band antenna. This antenna consists of two asymmetric L-shaped rectangular patches electrically connected by a single PIN diode. The proposed antenna operates at five frequency bands depending upon the switching states of the PIN diode. It operates at 2.4 GHz (WLAN) and 5.3 GHz (5G) during forward bias of the diode, 3.3 GHz (5G) and 5.9 GHz (WLAN) during reverse bias of the diode and 4 GHz during zero bias condition providing a wide bandwidth (3.6–4.8 GHz) at this state. The antenna has voltage standing wave ratio (VSWR) ranges from 1 to 2, gain value ranges from 2.6 to 5.0 dBi, and a maximum radiation efficiency of 85%. This antenna can be integrated with modern devices such as smart phones, laptops, and other handheld devices due to its simplistic geometry. A prototype of the model is fabricated, and the results are validated.

Measurement-based Investigation of the DC and RF Transconductance for Various HEMT Technologies in High-and Low-temperature Conditions

The purpose of this experimental study is to evaluate quantitatively the impact of the temperature on the behavior of various high electron-mobility transistor (HEMT) technologies through the analysis of the DC and RF transconductance. The experimental data are reported for six different HEMT devices, in order to develop a comparative analysis based on various technologies, including gallium arsenide (GaAs) and gallium nitride (GaN) materials, matched and pseudomorphic HEMTs, single- (S-H) and double-heterojunction (D-H) HEMTs, and both virgin and multi-layer devices. The reported findings show that the impact of the ambient temperature on the HEMT behavior strongly depend on the tested technology and operating conditions. As a matter of fact, a higher temperature can lead to increased or degraded transconductance, depending on the device technologies and bias point. In the GaAs-based devices, an operating bias condition at which the DC and RF transconductance are temperature insensitive can be defined, owing to two-opposite temperature-dependent effects counteracting with each other.

Exploring Reference Frame Integration Using Response Demands in a Tactile Temporal-Order Judgement Task

Exploring the world through touch requires the integration of internal (e.g., anatomical) and external (e.g., spatial) reference frames — you only know what you touch when you know where your hands are in space. The deficit observed in tactile temporal-order judgements when the hands are crossed over the midline provides one tool to explore this integration. We used foot pedals and required participants to focus on either the hand that was stimulated first (an anatomical bias condition) or the location of the hand that was stimulated first (a spatiotopic bias condition). Spatiotopic-based responses produce a larger crossed-hands deficit, presumably by focusing observers on the external reference frame. In contrast, anatomical-based responses focus the observer on the internal reference frame and produce a smaller deficit. This manipulation thus provides evidence that observers can change the relative weight given to each reference frame. We quantify this effect using a probabilistic model that produces a population estimate of the relative weight given to each reference frame. We show that a spatiotopic bias can result in either a larger external weight (Experiment 1) or a smaller internal weight (Experiment 2) and provide an explanation of when each one would occur.

Fabrication of A Diode-based Salt Solution Sensor

High blood pressure/hypertension is a severe medical issue among Malaysians that could be reduced by monitoring our salt/sodium intake. One way is to use intraoral salt sensor; this in-mouth method however may cause discomfort and adopts complex and costly fabrication processes. Hence, an external and reusable electronic device, that could be used as a “sweat-sensor”, is preferred in detecting the sodium intake of the body. In this study, a potentiometric diode-based salt solution sensor was designed and fabricated in order to detect different salt solution concentrations with applied external voltage. A p-n junction diode sensor was successfully designed and fabricated using four consecutive techniques; thermal wet oxidation, photolithography, thermal diffusion and metallization. The average sheet resistance and resistivity of the diode sensor were measured to be 3.50 x 105 ± 0.66 Ω⁄sq and 3.05 ± 0.5 Ωcm respectively. This sensor showed ideal I-V diode characteristics with a knee voltage of 11.5V in forward bias condition and breakdown voltage of -4 V in reverse bias condition. For salt concentration detection, the sensor was able to detect salt concentration changes with respect to current flow, up to 45 mg/mL.

A metamaterial loaded hybrid fractal multiband antenna for wireless applications with frequency band reconfigurability characteristics

In the present article authors propose the design and analysis of an octagonal shape multiband metamaterial loaded antenna with implementation of hybrid fractal geometry for wireless applications. Multiband features in the antenna structure is realized by applying the slotted and hybrid fractalization of Moore and Koch curve approach in radiating section along with introduction of two metamaterial SRR cells. The frequency band reconfigurability characteristics in proposed design is achieved by placing the PIN diode inside the connecting strip between the central hybrid fractal geometry and feedline. During forward bias condition of PIN diode antenna structure resonates at hepta (seven) band mode at WiMAX (3.5 GHz)/Lower C-band (4.41 GHz)/WLAN (5.4/5.8 GHz)/Lower X-band (8.26 GHz)/Upper X-band (10.48 GHz)/Lower Ku-band (13.35 GHz)/Middle Ku-band (14.42 GHz) wireless standards with S11 ≤ −10 dB. Proposed antenna represent the hexa and hepta band features during reverse bias (OFF-state) and forward bias condition (ON-state) of PIN diode respectively. A stable and consistent radiation patterns, appropriate impedance matching and an acceptable gain are achieved at all the operating frequencies of the proposed antenna.