Optical Properties of InGaN/GaN QW with the Same Well-Plus-Barrier Thickness

Optical properties of wurtzite violet InGaN/GaN quantum well (QW) structures, with the same well-plus-barrier thickness, grown by metal-organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates, were investigated using temperature-dependent photoluminescence (TDPL) and excitation-power-dependent photoluminescence (PDPL). Two samples were compared: one had a thicker well (InGaN/GaN 3/5 nm); the other had a thicker barrier (InGaN/GaN 2/6 nm). It was found that the GaN barrier thickness in the InGaN/GaN MQWs plays an important role in determining the optical characteristics of the MQWs. The peak energy of the two samples varied with temperature in an S-shape. The thicker-barrier sample had a higher turning point from blueshift to redshift, indicating a stronger localization effect. From the Arrhenius plot of the normalized integrated PL intensity, it was found that the activation energy of the nonradiative process also increased with a thicker barrier thickness. The radiation recombination process was dominated in the sample of the thicker barrier, while the non-radiation process cannot be negligible in the sample of the thicker well.

High-operating-temperature MWIR photodetector based on a InAs/GaSb superlattice grown by MOCVD

We demonstrate a high-operating-temperature (HOT) mid-wavelength InAs/GaSb superlattice heterojunction infrared photodetector grown by metal–organic chemical vapor deposition. High crystalline quality and the near-zero lattice mismatch of a InAs/GaSb superlattice on an InAs substrate were evidenced by high-resolution X-ray diffraction. At a bias voltage of –0.1 V and an operating temperature of 200 K, the device exhibited a 50% cutoff wavelength of ~ 4.9 μm, a dark current density of 0.012 A/cm2, and a peak specific detectivity of 2.3 × 109 cm·Hz1/2 /W.

Nanoindentation of Chromium Oxide Possessing Superior Hardness among Atomic-Layer-Deposited Oxides

Chromium (III) oxide is a technologically interesting material with attractive chemical, catalytic, magnetic and mechanical properties. It can be produced by different chemical and physical methods, for instance, by metal–organic chemical vapor deposition, thermal decomposition of chromium nitrate Cr(NO3)3 or ammonium dichromate (NH4)2Cr2O7, magnetron sputtering and atomic layer deposition. The latter method was used in the current work to deposit Cr2O3 thin films with thicknesses from 28 to 400 nm at deposition temperatures from 330 to 465 °C. The phase composition, crystallite size, hardness and modulus of elasticity were measured. The deposited Cr2O3 thin films had different structures from X-ray amorphous to crystalline α-Cr2O3 (eskolaite) structures. The averaged hardness of the films on SiO2 glass substrate varied from 12 to 22 GPa and the moduli were in the range of 76–180 GPa, as determined by nanoindentation. Lower values included some influence from a softer deposition substrate. The results indicate that Cr2O3 could be a promising material as a mechanically protective thin film applicable, for instance, in micro-electromechanical devices.

Optimization for the growth condition of In-situ SiNx cap layer on ultrathin barrier InAlGaN/GaN heterostructures by Metal-Organic Chemical Vapor Deposition

We investigate the dependence of material and electrical properties on the growth temperature of In-situ SiNx on InAlGaN/GaN heterostructures grown by Metal-Organic Chemical Vapor Deposition. Degradation of the interface between SiNx and InAlGaN layer was observed when growth temperature is below 900 ℃ or above 1100 ℃. With the optimized SiNx growth temperature, the high-quality SiNx and low interface trap density can be realized. Thus, the double-sweep capacitance-voltage measurement showed a sharp transition from charge accumulation to depletion with low hysteresis of 0.09 V. A small threshold-voltage shift after gate bias stress (1001 s) was also characterized by I-V measurement.

Using Modified-Intake Plasma-Enhanced Metal–Organic Chemical Vapor Deposition System to Grow Gallium Doped Zinc Oxide

We have used a modified-intake plasma-enhanced metal–organic chemical vapor deposition (MIPEMOCVD) system to fabricate gallium-doped zinc oxide (GZO) thin films with varied Ga content. The MIPEMOCVD system contains a modified intake system of a mixed tank and a spraying terminal to deliver the metal–organic (MO) precursors and a radio-frequency (RF) system parallel to the substrate normal, which can achieve a uniform distribution of organic precursors in the reaction chamber and reduce the bombardment damage. We examined the substitute and interstitial mechanisms of Ga atoms in zinc oxide (ZnO) matrix in MIPEMOCVD-grown GZO thin films through crystalline analyses and Hall measurements. The optimal Ga content of MIPEMOCVD-grown GZO thin film is 3.01 at%, which shows the highest conductivity and transmittance. Finally, the optimal MIPEMOCVD-grown GZO thin film was applied to n-ZnO/p-GaN LED as a window layer. As compared with the indium–tin–oxide (ITO) window layer, the n-ZnO/p-GaN LED with the MIPEMOCVD-grown GZO window layer of the rougher surface and higher transmittance at near UV range exhibits an enhanced light output power owing to the improved light extraction efficiency (LEE).

Phase Change Ge-Rich Ge–Sb–Te/Sb2Te3 Core-Shell Nanowires by Metal Organic Chemical Vapor Deposition

Ge-rich Ge–Sb–Te compounds are attractive materials for future phase change memories due to their greater crystallization temperature as it provides a wide range of applications. Herein, we report the self-assembled Ge-rich Ge–Sb–Te/Sb2Te3 core-shell nanowires grown by metal-organic chemical vapor deposition. The core Ge-rich Ge–Sb–Te nanowires were self-assembled through the vapor–liquid–solid mechanism, catalyzed by Au nanoparticles on Si (100) and SiO2/Si substrates; conformal overgrowth of the Sb2Te3 shell was subsequently performed at room temperature to realize the core-shell heterostructures. Both Ge-rich Ge–Sb–Te core and Ge-rich Ge–Sb–Te/Sb2Te3 core-shell nanowires were extensively characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman microspectroscopy, and electron energy loss spectroscopy to analyze the surface morphology, crystalline structure, vibrational properties, and elemental composition.