Advances in GaN Crystals and Their Applications

Abstract

This special issue looks at the potential applications of GaN-based crystals in both fields of nano-electronics and optoelectronics. The contents will focus on the fabrication and characterization of GaN-based thin films and nanostructures. It consists of six papers, indicating the current developments in GaN-related technology for high-efficiency sustainable electronic and optoelectronic devices, which include the role of the AlN layer in high-quality AlGaN/GaN heterostructures for advanced high-mobility electronic applications and simulation of GaN-based nanorod high-efficiency light-emitting diodes for optoelectronic applications. From the results, one can learn the information and experience available in the advanced fabrication of nanostructured GaN-based crystals for nano-electronic and optoelectronic devices.Keywords: GaN; AlN; InN; AlGaN; InGaN; MOSFET; LED Applications of GaN-Based CompoundsReviewing the application of semiconductor compounds, it stemmed from the replacement of vacuum tube by transistors in electronics [1,2]. The first "point-contact transistor" was invented by J. Bardeen and W. H. Brattain with "three-electrode elements" utilizing semiconductor materials, p-type, and n-type germaniums [1]. As the germanium crystal was substituted by silicon crystal to make a p-n-p bipolar junction transistor [3] or metal-oxide-semiconductor field effect transistor (MOSFET) [4], the electronic property of transistor was tremendously enhanced and the silicon-based electronic industry was then established. However, the VI-elements (i.e., Ge, Si) are basically indirect band structure, which is not suitable for the application of photo-electronic devices. When the IV-elements (Si or Ge) are replaced by GaAs-based III-V compounds, the electron mobility of MOSFET can be significantly increased [5] and quantum effects (e.g., normal and fractional quantum Hall effects) can be clearly detected [6,7]. In addition to the high-speed transistor applications, the direct band structures of GaAs-based III-V compounds extended the semiconductor materials to photo-electronic applications, in which the IV-elements (Si or Ge) are exclusive due to the indirect band structure. In such a way, the GaAs-based heterostructures were successfully utilized in the information and communication technology [8]. Moreover, many opto-electronic devices were invented with GaAs-compounds such as light-emitting diodes (LED) and laser diodes (LD). In other words, GaAs-based III-V compounds can be designed to apply in both electronic and opto-electronic devices. However, the light-sources made of GaAs-based compounds (group III-arsenides) were limited to the emitting photon wavelength greater than 760 nm (red light) due to the bandgap energy (i.e., E g = 1.424 eV of GaAs). On the other hand, the direct bandgap energy of group III-nitrides can cover the range from 0.7 eV (InN), 3.4 eV (GaN), to 6.2 eV (AlN). Therefore, the III-nitrides can offer a simple material system, replacing III-arsenides to integrate both electronic and opto-e...

Effect of magnetic field and impurities in InAs/GaAs and GaN/AlN self-assembled quantum dots

“…Due to its crystalline structure (zinc blende), these materials do not have a considerable piezoelectric field, so in this calculation it was disregarded. Subsequently, similar results will be presented for GaN/AlN QD's which have a geometry of truncated hexagonal pyramid [16,25] with dimensions from vertex to opposite vertex 18 (8) nm in its lower(upper) part, a height of 4.1 nm and a wetting layer of 1 nm. Finally, the results obtained by including impurities in both systems are given.…”

“…With the aim of determining how much these impurities affect the carrier states we have analyzed the effect of a single impurity in the studied systems. This is important for some applications such as optical devices and solar cells [6][7][8][9].…”