We consider a finite type-II superlattice with different dielectric media on either side of the surfaces, which consist of unit cells with alternating electron and hole layers in the unit cell. Under some assumptions, we have studied the density-density correlation function including overlap effects between electron and hole wave functions of adjacent layers using the random-phase approximation. We have obtained the dispersion relation for surface and bulk plasmons in a few cases. Furthermore, we have calculated the Raman intensity in order to compare the result with those of others.

Even though a patterned sapphire substrate (PSS) has been used for the growth of a high-quality epilayer because of its many advantages, it has not been successfully used to grow an AlN epilayer for ultraviolet (UV) light-emitting diodes (LEDs) on a PSS up to now. We report the growth of a high-quality AlN epilayer on a PSS, as a substrate for the manufacture of UV LEDs, by hydride vapor phase epitaxy (HVPE). The X-ray diffraction (XRD) peaks for the AlN epilayer grown on the PSS indicate that crystalline AlN with a wurtzite structure was grown successfully on the PSS. Furthermore, HVPE combining both in situ HVPE technology and liquid-phase epitaxy (LPE) using a mixed source is proposed as a novel method for the growth of a flat AlN epilayer on a PSS.

A finite HgTe/CdTe superlattice with different dielectric media on either side of the surfaces is investigated by taking into account the wavefunction overlap between the interface states and plasmons. The unit cell of the finite HgTe/CdTe superlattice consists of two electronlike states and a heavy-hole-like state in HgTe and two light-hole-like states in CdTe. Using the random-phase approximation added with some assumptions, we have studied the densitydensity correlation function by considering the interface state with the wavefunctions overlapping with the electron-like states, the light-hole-like states and the heavy-hole-like states. We have calculated the collective excitation spectra of the intrasubband and the intersubband for both the bulk plasmons and the surface plasmons as a function of the number of unit cells. The Raman intensities due to bulk and surface plasmons are expressed by the relative value of the mode energy of the plasmons.

High Al-composition AlGaN and AlN epilayers were grown directly on Si(111) substrate by a hydride vapor phase epitaxy (HVPE) method with a melted mixed source in a graphite boat set in a source zone with high temperatures of T = 700 and 800 °C, respectively. The presence of the Ga material in the mixed source of Ga and Al promoted the growth of AlN and AlGaN epilayers in the growth zone. When the temperature in the source zone was 800 °C, the crystalline quality of the AlN and AlGaN epilayers increased as the ratio of Ga to Al increased, and the optimum mix ratio of Ga to Al for the growth of AlN epilayers was approximately 0.35–0.42, obtained from a numerical fitting analysis of the X-ray diffraction (XRD) data for these epilayers. It appears that they can be grown directly by our melted-mixed-source HVPE method in a high-temperature source zone.

We developed a vertical-type light-emitting diode (LED) in which the substrate is removed using a hydride vapor phase epitaxy (HVPE) apparatus consisting of a multi-graphite boat filled with a mixed source and a high-temperature (T ≈ 900 °C) RF heating coil outside the source zone. The new chip-growth process with a significant reduction in the number of production steps is completed in only four steps, namely, photolithography, epitaxial layer growth, sorting, and metallization. We analyze the emission mechanism of these lights from measurement results to validate the characteristics of the light emitted from these vertical-type blue LEDs and white LEDs (WLEDs) without substrates, and propose that this mixed-source HVPE method may be a promising production technique for LEDs.