Advanced Semiconductor Laboratory
Developing cutting-edge technologies based on III-nitride semiconductors

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Monthly Archives: December 2016

Knowledge you should know about LED

Renad AlJefri - December 29, 2016

Light emitting diodes are lighting our lives and are ten times more efficient than the century-old great light bulb. Both are made and optimized with the knowledge of electromagnetics. It is true that Edison did not need to solve Gauss’s law to build an incandescent light, but to understand the colors of light you need to understand Planck's law of black-body radiation which is derived from energy distribution of photons gas in thermal equilibrium. ​
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Brief of MOSCAP

Sarah Alsaggaf - December 27, 2016

There are four essential devices in integrated circuits (IC) which are resistors, diodes, capacitors, and transistor. In general, a capacitor is a device that has two closely spaced conductors, which are called plates, separated by an insulator or a dielectric material such as air, foil or any other insulation. The function of the capacitor is to store the energy in the electric field between these plates; so it works as energy-storage in any device.  

Current Status of DUV Laser

Ronghui Lin - December 26, 2016

To date, the development of DUV laser diode is still at its early stage. DUV laser diodes are still in the lab, far from mass production. Most of these attempts make use of the AlGaN/AlN material ​system, which is one of the promising material systems that can be used to produce DUV laser with high performance. There are generally three methods to pump the laser diode:​​​​

 

High Temperature MOCVD grown AlGaN\AlN epilayers

Hamad S. Alotaibi - December 26, 2016

AlGaN material has been demonstrated as a promising candidate for UV devices. High-quality AlGaN is preferably grown on AlN\sapphire buffer layer over GaN\sapphire. AlGaN\GaN will suffer from a biaxial strain after exceeding a critical thickness due to the lattice mismatch between the AlGaN and GaN, especially with high Al composition [1]. Also, GaN template is not recommended for UV devices due to its high absorption of UV light.

Showerhead design for MOCVD

Kuang-Hui Li - December 26, 2016

​For MOCVD deposition, precursors will thermally decompose, then diffuse onto the substrate. However, there is an unfavorable process called parasitic reaction if a chemical reaction happens within precursors.

Gallium Oxide: a new semiconductor candidates for high power electric device

Feng Wu - December 26, 2016

Gallium oxide has attracted a considerable interest as a functional material for various applications. In these applications, high power high voltage electric device is very appealing because of its high breakdown voltage. The breakdown voltage can reach above 1000 V as shown in the Fig. 1. Besides, it is also attractive from an industrial viewpoint since large-size, high-quality wafers can be manufactured from a single-crystal bulk synthesized by melt–growth methods.

Microscale energy harvesting

Nasir Alfaraj - December 25, 2016

Recent advances in nanotechnology have enabled rapid integration of microscale electronic energy-harvesting devices such as solar cells, thermoelectric and piezoelectric generators, and fuel cells. Due to their low-cost material and manufacturing advantages, these nanostructured devices are typically fabricated using solution processing methods and have the potential for growth while achieving an efficient energy-harvesting rate.

Cathodoluminescence and electron source

Wenzhe Guo - December 24, 2016

Over the last few years, the III-nitride AlGaN materials have been used to achieve deep ultraviolet laser sources, which triggers many new developments in various domains. However, realizing high-performance deep UV laser based on current injection and optical pumping remains challenging since p-doping and ohmic contact formation are difficult to achieve and inefficient. An alternative approach is in the case of cathodoluminescence based on electron beam pumping. Cathodoluminescence is the emission of photons of characteristic wavelengths by high energy electron beam bombarding semiconductor material. But to realize a compact and portable deep UV laser pumped by e beam still remains unavailable.

Difficulty in predicting the accurate bandgaps of semiconductors

Muwei Zhang - December 24, 2016

Band structures always play a very important role in materials application or devices design. It reveals the basic electronic properties like bandgaps, effective masses, etc. For decades, as a computer method of predicting the materials properties, the first principle calculation can give us very satisfied results such as total energy, Fermi levels, showing good agreements with the experiments. However, the theoretical description of band structures by the first principle calculation remains a very challenging problem, mainly due to the inaccuracy of density function exchange correlations.

New laser applications

Altynay Kaidarova - December 19, 2016

​Since 1960 lasers have driven scientific innovation into a facet of modern life. Many scientific, military, medical and commercial laser applications were developed since then. The question is whether the laser is going to continue to drive such advances in the future.
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