#quantum wells

MXene-GaN van der Waals metal-semiconductor junctions for high performance photodetection

High levels of dark current and noise have ailed metal-semiconductor-metal (MSM) photodetectors for years. Recently, scientists in China demonstrated that by replacing conventional metals with MXene, the dark current and noise of MSM multiple quantum well photodetectors can be significantly improved.

The proliferation of the Internet of Things (IoT) has sparked intense interest of photodetectors (PD) as they are widely used in sensing, detection, data transport and processing. The coming 5G-enabled IoT (5G-IoT) will require new performance criteria such as massive connectivity, ultra-low latency and ultra-reliability for huge number of IoT devices. To meet these demands, metal-semiconductor-metal (MSM) photodetectors have received much attention for their high response speed, simple fabrication process and feasibility of integration with field effect transistor (FET) technology.

However, the conventional fabrication process will induce chemical disorder and defect states at the metal-semiconductor interfaces, leading to significant dark current and noise. Additionally, opaque metals are usually placed on top of the active light absorption region, which will reflect part of the incident light and thus reduce the responsivity of MSM photodetectors.

New 2-D Ruddlesden-Popper (RP) layered perovskite-based solar cells

In recent years, researchers worldwide have been trying to develop solar cells and other technologies that can produce electrical energy from renewable sources, as these could reduce the emission of greenhouse gases and thus help to preserve life on our planet. Solar cells can be built using a variety of materials, including silicon, copper or other semiconductors.

Another class of materials that has proved to be highly promising for the fabrication of solar cells are perovskites, calcium titanium oxide minerals that can be extracted from the Earth's mantle in specific geographical regions. This includes 2-D Ruddlesden-Popper (RP) perovskites, which have a unique structure that could enhance a device's environmental stability and optoelectronic properties, without significantly compromising its efficiency.

Generally, 2-D RP perovskites have multiple quantum wells (QWs) with a random well width distribution, which can impair the thermodynamic stability of perovskite solutions. QWs are thin layers that confine particles in the dimension perpendicular to the surface of a given layer in a device (e.g., in a well-like space) , without restricting movement in other dimensions.

Scientists go deep to quantify perovskite properties

Study of excitons important to next-generation electronics

Scientists led by Rice University and Los Alamos National Laboratory have discovered electronic properties in quantum-scale devices that are likely to impact the growing field of low-cost perovskite based optoelectronics.

In an open-access Nature Communications paper, researchers led by Los Alamos scientists Aditya Mohite and Jean-Christophe Blancon, both of whom will join Rice this summer, studied the behavior of excitons trapped in quantum wells made of crystalline, halide-based perovskite compounds.

As a result, they were able to create a scale by which labs can determine the binding energy of excitons, and thus the band gap structures, in perovskite quantum wells of any thickness. This could in turn aid in the fundamental design of next-generation semiconductor materials.

Perovskite quantum well-based optoelectronic devices convert and control light at the quantum scale, reactions below 100 nanometers that follow different rules from those dictated by classical mechanics.

Plasmon-powered devices for medicine, security, solar cells under development

A Rice University professor's method to "upconvert" light could make solar cells more efficient and disease-targeting nanoparticles more effective.

Experiments led by Gururaj Naik, an assistant professor of electrical and computer engineering, combined plasmonic metals and semiconducting quantum wells to boost the frequency of light, changing its color.

In a nanoscale prototype Naik developed as a postdoctoral researcher at Stanford University, custom-designed pylons that were struck by green light produced a higher-energy blue glow. "I'm taking low-energy photons and converting them to high-energy photons," he said.

Efficient upconversion of light could let solar cells turn otherwise-wasted infrared sunlight into electricity or help light-activated nanoparticles treat diseased cells, Naik said.

The work appears in the American Chemical Society's Nano Letters.