High quality quantum wire (QWR) structures with an emitting wavelength in the 1.5-μm range were self-organized in an In0.65Ga0.35As/In0.52Al0.48As quantum well layer grown on a (775)B-oriented InP substrate by molecular beam epitaxy. Photoluminescence (PL) from the (775)B In0.65Ga0.35As/In0.52Al0.48As QWRs with a nominal well width of 4.8 nm was observed at 1.43 μm at 12 K, which corresponds to a PL wavelength of about 1.5 μm at room temperature. The PL peak was considerably polarized along the wire direction with a polarization degree of P [= (I∥ - I⊥) / (I∥ + I] ⊥)] = 0.14, indicating its good one-dimensionality. The FWHM of the PL peak was as small as 17 meV, which is the best value for InGaAs QWRs on InP substrates.

ZnO (ZO) and Aluminum (Al) doped ZnO (AZO) films were grown on sapphire substrate via oxygen radical assisted molecular beam epitaxy (MBE) technique. The results of XRD measurement and temperature dependent Hall measurement confirmed that the AZO films were typically highly degenerate semiconductor with good crystallinity. The resistivity of these films were closed to the theoretical lower limit. The optical properties of these films were investigated by photoluminescence (PL) spectra and absorption spectra. Strong band-edge emission was observed in the AZO films with good crystallinity in spite of high carrier concentration more than 1020 cm-3. A sift of absorption edge to higher energy side and a gradual increase of the absorption was observed for the AZO film.

In the present work, we examine the formation of defects on the sidewall slope in 1 μm - thick GaAs layers regrown on GaAs/AlGaAs heterostructures. Site-specific TEM specimens of sidewall slopes are obtained using focused ion beam combined with lift-out method. TEM analysis shows planar defects, such as stacking faults and microtwins, dislocations and large twinned areas, nucleating on the AlGaAs surfaces. SIMS and EDX reveal an increase in carbon and oxygen at the interface. The defect density increased with Al content exceeding 1010 cm-2 on Al0.4Ga0.6As. The defect formation is related to the oxidation of Al-containing surfaces.

The SiGe:C hetero-structure bipolar transistor (HBT) has turned into a key technology for wireless communication. This paper describes the metrology tools for SiGe epitaxy process control. Two types of analysis are critical, (1) routine control of SiGe base and Si cap thicknesses, location and thickness of the doping layer, doping dose, Ge composition profile, and their uniformity across the wafer; and (2) root-cause analysis on non-routine problems. This is achieved by developing a transmission electron microscopy (TEM) technique allowing a thickness measurement with a reproducibility better than 3 Å. Charge-compensated low-energy secondary ion mass spectrometry (SIMS) using an optical conductivity enhancement (OCE) allows a Ge composition measurement to a required precision of 0.5 at. %.

We have studied the emission from LEDs based on GaInNAs Quantum Wells (QWs) and InAs Quantum Dots (QDs) as a function of temperature and current. It is found that the carrier loss in GaInNAs QWs is dominated by non-radiative monomolecular and Auger processes resulting in an external quantum efficiency of only 0.08 % at 10 °C and 1000 A cm-2. In contrast, the InAs QDs have a higher external quantum efficiency, peaking at 0.8 % at 10 °C and 5 A cm-2, but this value rapidly decreases as the excited states of the QDs are filled and Auger-like processes become dominant. These results highlight the issues that must be addressed if these materials are to find commercial application: namely, the areal density of QDs must be increased and the material quality of the GaInNAs QWs must be improved.

In accord with the Drude model, the free-carrier contribution to the dielectric function at infrared wavelengths is proportional to the ratio of the free-carrier concentration N and the effective mass m*, and the product of the optical mobility μ and m*. Typical infrared optical experiments are therefore sensitive to the free-carrier mass, but determination of m* from the measured dielectric function requires an independent experiment, such as an electrical Hall-effect measurement, which provides either N or μ. Highly-doped zincblende III-V-semiconductors exposed to a strong external magnetic field exhibit non-symmetric magnetooptical birefringence, which is inversely proportional to m*. If the spectral dependence of the magnetooptical dielectric function tensor is known, the parameters N, m* and μ can be determined independently from optical measurements alone. Generalized ellipsometry measures three complex-valued ratios of normalized Jones matrix elements, from which the individual tensor elements of the dielectric function of arbitrarily anisotropic materials in layered samples can be reconstructed. We present the application of generalized ellipsometry to semiconductor layer structures at far-infrared wavelengths, and determine the magnetooptical dielectric function for n-GaAs and n-AlGaInP for wavelengths from 100 μm to 15 μm. We obtain the effective electron mass and mobility results of GaAs in excellent agreement with results obtained from Hall-effect and Shubnikov-de-Haas experiments. The effective electron mass in disordered n-AlGaInP obtained here is in very good agreement with previous k·p calculations. (Far)-infrared magnetooptic generalized ellipsometry may open up new avenues for non-destructive characterization of free-carrier properties in complex semiconductor heterostructures.

The evolution of sheet resistance (Rs) of p-type conductive GaAs(1-x)Nx epilayers (x = 0.6%, 1.4%, and 2.3%) exposed to MeV 1H+, 7Li+, 12C+, and 16O+ ions and the stability of the formed electrical isolation during post-irradiation annealing were investigated. Results show that the threshold dose (Dth) to convert a conductive layer to highly resistive one close-to-linearly depends on original free carrier concentration and inversely depends on the number of irradiation-generated atomic displacements, and is independent of the nitrogen content in GaAsN layers. Increasing beam flux of 12C+ results in a lower Dth, whereas 1H+ beam flux does not affect it, showing the influence of collision cascade density. Results also show that irrespectively of the ion mass, the stability of electrical isolation formed in GaAsN is dependent on the ratio of the concentration of irradiation-created carrier traps to Dth. The electrical isolation can be preserved up to 550°C when the accumulated dose (D) is greater than 3.3 Dth.

In this study, we used differential scanning calorimetry (DSC) to study pyrolysis kinetics of zinc acetylacetonate (Zn(acac)2) in chamber ambient simulating real CVD condition, with heating rate from 10 to 20 °C/min. For Zn(acac)2 heated in pure N2, inert environment, DSC showed three endothermic peaks locating at 91–106 °C, 121–128 °C, and 135–142 °C, with peak area being 88 KJ/mol, 14 KJ/mol, and 18 KJ/mol, respectively. The DSC residuals analyzed by IR indicated all peaks might be originated from physical phenomena, since no compositional change observed. Further study by temperature programmed polarized optical microscope (POM) showed these peaks might be related to dehydration, phase transition, and melting of Zn(acac)2 and its hydrates. DSC in oxygen-containing ambient with O2 concentration from to 13 to 40 % showed three endothermic peaks and two additional exothermic broad peaks at higher temperature, 209–236 °C, and 330–400 °C. These exothermic peaks are assigned to oxidative decomposition of Zn(acac)2 and releasing of ligands. When oxygen concentration increased, peak area grew. Positions of these peaks depend on heating rate. Increasing the heating rate caused every peak to shift toward higher temperatures, with the first two endothermic peaks merged into one broad one.

IV-VI compound semiconductors are of interest due to their potential application as thermoelectric material, infrared detectors and semiconductor lasers. The use of PbTe based semiconductors is usually in the middle and far infrared region. Magnetron sputtering of PbTe thin films from a single target on Si (111) was performed under various conditions. Characterization of the films shows that PbTe films on Si (111) substrate are suitable for preparation of infrared (IR) detectors. By heat treatment novel IR detectors can be developed in the electron absorption region of 4 – 10 μm.

Based on the AlxGa1-xAs/GaAs system and with graded Distributed Bragg mirrors (DBRs), a VCSEL for operation at 850–860nm is reported. The graded transition bands inside the DBRs were designed in order to achieve the tradeoff between the number of DBR layers and the low threshold current of the laser. The structure optimized had 39 pairs in the n-DBR stack and a low threshold current of 1.6mA was achieved. The device was fabricated with MBE growth, oxide confinement and RIE for MESA definition. The experimental results and physical characterization of the device are also reported to fully understand the VCSEL performance. The threshold current and other parameters predicted by the simulation are in good agreement with experimental results.

This paper reports preparation of highly oriented (002) ZnO films by atmospheric pressure CVD at 320°C, which is far below previous reported values. In this study, a cold wall horizontal system was used to thermally decompose sublimed zinc acetylacetonate (Zn(acac)2, Zn(C5H702)2) vapor, and reacted with water vapor to produce ZnO films at temperatures above 320°C. Through experimental data, we discovered that low deposition temperature, using water vapor as co-reactant and substrates with ZnO buffer layer pre-coated by PVD are the key factors to prepare (002) ZnO films. By using Si(100) pre-coated with sputtered ZnO amorphous buffer layer as substrates, the ZnO growth rate is highest. While using copper oxide pre-coated Si substrates gave the lowest growth rate, and deposited ZnO film is amorphous. Considering influence of CVD co-reactant, using Zn(acac)2 and water vapor gives higher growth rate and better crystallinity than CVD using Zn(acac)2 and oxygen. Water vapor may supply hydrogen to react with released acetylacetonyl ligand (C5H7O2), and help the formation of stable acetylaceton (C5H8O2) molecule. DPA shows that film contain 46% O and 54% Zn. XPS of Zn Auger identified the valence of Zn being Zn2+. It seems that excessive Zn might present as discrete Zn2+ dispersed between ZnO lattices.

Room-temperature Er-related electroluminescence (EL) properties have been investigated in Er,O-codoped GaAs (GaAs:Er,O) light emitting diodes (LEDs) grown by organometallic vapor phase epitaxy (OMVPE). Under forward bias, characteristic emission due to a luminescence center consisting of Er coordinated by O and As was clearly observed at room temperature, while the Er-related EL was undetectable under reverse bias. At lower current densities, the EL intensity increased linearly with the current density. Subsequently, the intensity exhibited a tendency to saturate at higher current densities. By analyzing the behavior with a fitting according to rate equations, the excitation cross section of Er ions due to current injection was determined to be approximately 10-15 cm2, which is by five orders in magnitude larger than that for optical excitation in Er-doped fiber amplifiers (10-20∼10-21 cm2).

The incorporation mechanism of oxygen into MBE-grown AlGaAs layers was systematically studied by changing the growth temperature and AlAs mole fraction. It was found that segregation of oxygen atoms strongly influences oxygen incorporation. By taking into account the surface segregation of oxygen, all of the particular characteristics observed in the oxygen incorporation into MBE-grown AlGaAs layers can be explained including a peak and a dip formation in the profile. Oxygen atoms accumulate on the surface of the substrate due to surface segregation and the number multiplied by the coefficient of surface segregation determines the oxygen incorporation.

The effects of high gate voltage Vg stress on the stability of non-hydrogenated and hydrogenated short p-channel polysilicon thin-film transistors (TFTs) are investigated for operation in the saturation region. The degradation mechanisms were identified from the evolution with stress time of the static device parameters. In non-hydrogenated TFTs, transconductance overshoot and a turnover behavior in the threshold voltage were observed. The results indicate that hot-electron trapping near the drain dominates in the initial stages of stress and channel holes are injected into the gate oxide followed by interface states generation as the stress proceeds further. In hydrogenated TFTs, first an effective shortening of the channel length is observed due to trapping of hot-electrons. As the stress proceeds further, donor-type interface states are generated and the electric field near the drain increases due to built-up of positive charge resulted from trapping of hot-holes in these states.

In the paper, Cd1-xZnxTe polycrystalline films have been prepared by co-evaporation, which can control the zinc content, using CdTe and ZnTe as the evaporation sources. The cubic phase in these films as-deposited and annealed has been demonstrated by XRD. The XRD peaks of Cd1-xZnxTe films are always between the corresponding peaks of CdTe and ZnTe. According to Vegard Formula, x values of Cd1-xZnxTe films have been confirmed from XRD data, which shows that both the calculated and experimental x values are almost identical. The optical transmission of Cd1-xZnxTe films has been measured, and the optical energy gaps have been calculated from the transmission. The band gaps vary in a quadratic way with x values, and increase with annealing temperatures. When application of Cd1-xZnxTe film as a buffer of around 80nm thick in CdS/CdTe solar cells, the structure of the cells becomes CdS/CdTe / Cd1-xZnxTe / ZnTe:Cu and their average conversion efficiency is improved by 40% where x is in the range of 0.55 to 0.65. The mentioned above results are discussed.

The DC and RF characteristics of In0.5Ga0.5P/In0.22Ga0.78As/GaAs MOS p-HEMTs with different gate oxide thickness were investigated and compared with those of Schottky-gate p-HEMT without the gate oxide layer. The oxide layer was implemented by using a liquid phase oxidation technique. It was found that transconductance (gm), threshold voltage and breakdown voltage characteristics of MOS p-HEMTs depended strongly on the gate oxide thickness. The MOS p-HEMTs showed superior DC and RF performances compared with those of GaAs-based MOSFET having oxide/n-GaAs or oxide/InGaAs interface.

The photo-field emission properties of semiconductors at a very strong electric field together with tunnel electron emission in metal-insulator-semiconductor heterostructures with a tunneltransparent layer of an insulator was studied. It was found that a self-consistent quantum well near the surface of semiconductor emitter tips can change the spectral region of photosensitivity of the radiation semiconductor field emitter detectors, and leads to the significant increase in their photosensitivity [1]. Also the appearance of a self-consistent quantum well near the semiconductor surface is the key factor which allows to use the metal-insulator heterojunction in the development of an Auger transistor based on the Al-SiO2-n-Si structure - the fastest operation semiconductor bipolar transistor [2–4]. Conditions for appearance of a self-consistent quantum well under strong electric field in both the near-surface region of a vacuum semiconductor field-emitter and metal-insulator-semiconductor heterostructures (Auger transistor) were studied also.

Epitaxial-transparent-substrate light emitting diodes with a primary emission peak at 590nm and a secondary peak at 560nm have been fabricated in the indium aluminum gallium phosphide (InAlGaP) system. The active layer consists of an undoped, compressively strained indium gallium phosphide (InGaP) quantum well on a transparent In0.22(Al0.2Ga0.8)0.78P/ ∇x[1nx(Al0.2Ga0.8)1-xP] /GaP virtual substrate. Theoretical modeling of this structure predicts an accessible wavelength range of approximately 540nm to 590nm (green to amber). Emission with a peak wavelength of 570nm has been observed via cathodoluminescence studies of undoped structures with a quantum well composition of In0.35Ga0.65P. Light emitting diodes have been fabricated utilizing simple top and bottom contacts. The highest LED power of 0.18μW per facet at 20mA was observed for a quantum well composition of In0.32Ga0.68P and a bulk threading dislocation density on the order of 7×106 cm-2. The spectrum of this device was composed of two peaks: a weak peak at the predicted 560nm wavelength and a stronger peak at 590nm. Based upon superspots present in electron diffraction from the quantum well region, we believe that the observed spectrum is the result of emission from ordered and disordered domains in the active region. The same device structure grown with a bulk threading dislocation density on the order of 5×107 cm-2 exhibited an identical spectral shape with a reduced power of 0.08μW per facet at 20mA. For a quantum well composition of In0.37Ga0.63P and an overall threading dislocation density on the order of 5×107 cm-2, a single peak wavelength of 588nm with a power of 0.06μW per facet at 20mA was observed.

Characteristics of the ZnO and ZnMgO films grown by radical-source molecular beam epitaxy are reported. The ZnO films on a-plane sapphire substrates had a superior quality in crystallographic, optical and electrical properties, and n-type doping with Al was successfully performed up to 1020 cm–3. The Mg-content of ZnMgO alloys was found to be controlled by a simple growth mechanism as a function of Mg-cell temperature. The alloying in the ZnO-rich region resulted in single-crystalline growth although the photoluminescence characteristics at x = 0.22 suggested the presence of microscopic phase separation. Single-crystalline growth was also achieved on Si (111) substrates by using a CaF2 buffer layer to protect the Si-surface from oxidation.

Erbium (Er) ions were co-implanted with ytterbium (Yb) into Al0.70Ga0.30As substrates and we realized an increase in the intensity of Er intra-4f-shell luminescence. The photoluminescence (PL) intensity of Er-related dominant peak (1538.2nm) was enhanced by co-implanted Yb. The thermal quenching was improved. PL intensity of Yb-related emission was decreased. We studied the transfer energy and the optical sensitization of Yb ions co-implanted with Er ions in Al0.70Ga0.30As. Energy transfers from 2F5/2 (the first excited state) → 2F7/2 (the ground state) of Yb3+ to 4I13/2 (the first excited state) → 4I15/2 (the ground state) of Er3+ were observed by PL excitation (PLE) and selectively excited PL (SPL).