Optimization of Dry and Wet GaN Etching to Form High Aspect Ratio Nanowires

Nanowire devices are emerging as the replacement technology to planar devices, such as Light Emitting Diodes (LEDs) and Field Effect Transistors (FETs), due to better performance and higher device densities. Here, top-down GaN nanowire fabrication is studied through the use of dry and wet etching techniques. Specifically, dry etching is studied focusing on the effects of etching power, pressure, and the use of chloroform during the process. Wet etching of GaN nanowires takes the initial structures formed by the dry etch to create the desired high aspect ratio, tunable-diameter nanowires. Effects of etching time, temperature, concentration, and ability to remove etch damage are thoroughly studied. Insights of these results are utilized to form high aspect ratio vertical wires with diameters smaller than 100 nm for high performance GaN devices

Advanced III-Nitride LEDs for Display Applications

Gallium Nitride (GaN) light emitting diodes (LEDs) are viewed as the next generation of display technology as a replacement for both liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays. GaN based LEDs offer immense improvements in terms of efficiency, reliability, and resolution as compared to these conventional display technologies. New device opportunities are presented with the advent of LED displays, however there are a number of key challenges that also need to be addressed. Displays rely upon transistors in order to individually control the brightness of each color in a pixel. LED displays are no different, though there are no straightforward ways to pair transistors with LEDs. Furthermore, LEDs still leave room for improvement, suffering from poor p-type activation, single color emission, and inflexibility. Though with the promise of GaN LEDs, new integration approaches are realized here to overcome these limitations. To address the challenge of transistors and LEDs, an innovative integration between LEDs and field effect transistors (FETs) has been demonstrated. The integrated LED-FET devices lead to dramatic increases in resolution, substantial decreases in processing steps, and considerable area savings. Device and simulation results are presented, with further scaling optimizations outlined. The idea of full color integration has been a challenge for LEDs, where often multiple material systems are combined in order to realize these displays. Multiple materials translate to higher costs and lower resolution, as separate fabrication is performed to create these LEDs and then transfer the LEDs together. Monolithic approaches have been pursued, though necessitate the use of rare-earth materials. Instead, the structure of the LED is exploited in order to create the full range of LED colors from red to blue in a simple, efficient, monolithic format to demonstrate multi-color µ-LEDs. Several novel devices and integration schemes are also presented that expand upon the existing device applications. Work developing a novel nanowire lift-off mechanism is presented which allows for both substrate reuse, as well as flexible devices. A capacitor-LED integration mechanism is demonstrated to enhance hole activation and utilization. AC operating LEDs are demonstrated through tunneling. Integration of high-power devices are additionally investigated for driving higher power LEDs. Together these breakthroughs provide a pathway for LED displays and beyond

Corrections to “Demonstration of Trench Isolated Monolithic GaN µLED Displays Enabled by Photoresist Planarization”

Presents corrections to the article “Demonstration of Trench Isolated Monolithic GaN µLED Displays Enabled by Photoresist Planarization”

The relative importance of complexity, variety, and portion size in ice cream preference in Dutch and American participants

Food variety, complexity, and portion size each influence food choice and consumption, but their relative importance is poorly understood. In an online discrete choice-experiment, we investigated the relative importance of variety, complexity, and portion size in consumer preferences by systematically varying ice cream offerings. Complexity was defined as the presence of different components within a scoop (e.g., chunks or flavors), while variety was defined as combinations of ice cream scoops that differ in flavor and/or texture. A choice-based conjoint questionnaire with two sections was presented to 498 Dutch (50.8% females) and 502 American (52.6% females) consumers aged between 18 and 65 years. Section 1 tested the relative importance of complexity and variety in consumer preferences, while Section 2 tested the relative importance of variety and portion size in preferences. Participants chose their preferred option when presented with various ice cream options showing different levels of variety and complexity (Section 1), or different levels of variety and portion sizes (Section 2). Across countries, variety was a stronger driver of ice cream preference than complexity, but the most preferred ice cream options were both varied and complex. Further, across countries, flavor was more important than portion size, and again a variety of flavors was the most preferred. Finally, American participants overall preferred larger portion sizes than did Dutch participants. These data indicate variety is a key determinant of food preference, at least within the context of this study, for consumers in both the Netherlands and the United States

Eating rate and bite size were related to food intake across meals varying in portion size: A randomized crossover trial in adults

Serving larger portions leads to increased food intake, but behavioral factors that influence the magnitude of this portion size effect have not been well characterized. We investigated whether measures of eating microstructure such as eating rate and bite size moderated the portion size effect. We also explored how sensory-specific satiety (SSS; the relative hedonic decline of a food as it is eaten) was affected by eating microstructure and larger portions. In a randomized crossover design, 44 adults aged 18-68 y (66% women; 46% with overweight and obesity) ate lunch in the laboratory once a week for 4 weeks. The meal consisted of pasta that was varied in portion size (400, 500, 600, or 700 g) and 700 g of water. Meals were video-recorded to assess bite count and meal duration, which were used to calculate mean eating rate (g/min) and mean bite size (g/bite). At each meal participants also completed an assessment of SSS. The results showed that as larger portions were served, meal intake increased in a curvilinear manner (p 0.10). In summary, the portion size effect was not moderated by eating microstructure, but relatively faster eating rates and larger bite sizes at meals, along with large portions, combined to increase food intake

Does labelling a food as 'light' vs. 'filling' influence intake and sensory-specific satiation?

Although several studies have investigated the influence of nutrition labelling on food intake, the effect of labels indicating a food's satiating power on food intake and sensory-specific satiation (SSS) is poorly understood. We investigated whether providing information about the satiating power of a meal affects intake and SSS. Participants (19 men and 18 women) consumed the same test meal of pasta salad ad libitum on two occasions, once described as 'light' and once as 'filling'. SSS was determined as the change in liking of the flavor and desire to eat the test meal before and after consumption, compared to seven uneaten foods. As hypothesized, intake increased by a mean (±SD) of 31 ± 59 g and 42 ± 81 kcal when the meal was labelled 'light' as opposed to 'filling' (p < 0.01). After eating, ratings for both liking and desire to eat decreased significantly more for the test meal than for the uneaten control foods (p < 0.001), demonstrating SSS. These relative changes in liking and desire to eat did not differ between the label conditions, despite differences in intake. Furthermore, accounting for amount consumed, the magnitude of SSS did not differ between the label conditions, which suggests that it did not explain the effect of the labels on intake. This study shows that labels indicating the satiating power of a meal can affect intake, warranting caution in the use of such labels on products intended to reduce intake