A complete description of Szep's (2,p)- semifields

Abstract

Simultaneous determination of indium and nitrogen contents of InGaAsN quantum wells by optical in situ monitoring

In situ monitoring of metal-organic vapor phase epitaxialgrowth of InGaAsN∕GaAs multiquantum wells is studied. The complex refractive index of InGaAsN is determined for several indium and nitrogen contents based on the fits to the reflectance curve. Taking advantage of the different effects caused by the incorporation of indium and nitrogen on the complex refractive index of InGaAsN, the InGaAsN quantum well nitrogen and indium contents are simultaneously determined in situ.Peer reviewe

Doping and carrier transport in Ga1-3xIn3xNxAs1-x alloys

Si- and Be-doped Ga1-3xIn3xNxAs1-x (0 less than or equal tox less than or equal to 3%) layers are grown on GaAs substrates by gas-source molecular beam epitaxy with a nitrogen radical beam source. The carrier concentration and mobility are observed to decrease substantially with increasing nitrogen content in both p- and n-type GaInNAs films. After rapid thermal annealing at 750 degreesC, the Be dopants are almost fully activated in p-type material; yet only a small fraction of the Si dopants are activated in n-type GaInNAs films. At low temperature a broad photoluminescence band centered at 1.041 eV (about 120 meV below the band gap) is observed in n-type GaInNAs, which suggests the possible compensating centers present in Si-doped GaInNAs.Peer reviewe

Self-assembled GaIn(N)As quantum dots: Enhanced luminescence at 1.3 µm

Self-assembled GaIn(N)As quantum dots are fabricated on GaAs by atmospheric pressuremetalorganic vapor-phase epitaxy using dimethylhydrazine (DMHy) precursor as a nitrogen source. The incorporation of nitrogen into the islands is observed to be negligible. However, the areal density of the islands is increased by up to one order of magnitude compared to that of the respective GaInAs islands. The GaIn(N)As island size can also be controlled by varying the DMHy flow. An enhancement of the room-temperature luminescence at 1.3 μm is observed in the GaIn(N)As samples grown with DMHy.Peer reviewe

Morbidity and Causes of Death in Patients with Cutaneous T-cell Lymphoma in Finland

Cutaneous T-cell lymphomas (CTCL), especially mycosis fungoides, can be considered as a state of longstanding low-grade systemic inflammation. Many studies have focused on secondary cancers with CTCL, but information about comorbidities is limited. A total of 144 patients with CTCL at Helsinki University Central Hospital during 2005 to 2015 were studied to determine associated comorbidities and causes of death in this cohort. Compared with an age-standardized control population, the prevalence of type 2 diabetes mellitus was increased among patients with CTCL with no link to obesity. Patients with CTCL had a lower prevalence of hypertension, myocardial infarction and stroke than the control group. The 3 most common causes of death were CTCL, coronary artery disease and lung cancer. The increased risk of myocardial infarction or stroke reported previously was not detected in this patient group.Peer reviewe

In situ determination of InGaAs and GaAsN composition in multiquantum-well structures

Metal-organic vapor phase epitaxialgrowth of InGaAs/GaAs and GaAsN/GaAs multiquantum-well (MQW) structures was monitored by in situ reflectometry at 635 nm using a normal incidence reflectance setup. The reflectance signal is found to change significantly during both quantum-well (QW) and barrier growth regions. A matrix method is used to calculate the theoretical reflectance curve and comparing the theoretical curves to the measured ones the complex refractive index of the ternary alloys are derived. Consequently, when the behavior of the complex refractive indices of InGaAs and GaAsN is known as a function of composition, the composition of all the QWs in the MQW strucure can be determined in situ.Peer reviewe

Temperature dependence of carrier relaxation in strain-induced quantum dots

We report experimental observation and theoretical interpretation of temperature-dependent, time-resolved luminescence from strain-induced quantum dots. The experimental results are well described by a master equation model for the electrons. The intraband relaxation in the conduction band and the radiative recombination rate are governed by the hole populations resulting in prominent temperature dependence of the relaxation process. Even when only a few electrons and holes are confined in a single quantum dot the Auger-like process provides a rapid intraband relaxation channel for electrons that can replace the phonon scattering as the dominant relaxation mechanism.Peer reviewe

Comparison of ammonia plasma and AlN passivation by plasma-enhanced atomic layer deposition

Surface passivation of GaAs by ammonia plasma and AlN fabricated by plasma-enhanced atomic layer deposition are compared. It is shown that the deposition temperature can be reduced to 150 °C and effective passivation is still achieved. Samples passivated by AlN fabricated at 150 °C show four times higher photoluminescence intensity and longer time-resolved photoluminescence lifetime than ammonia plasma passivated samples. The passivation effect is shown to last for months. The dependence of charge carrier lifetime and integrated photoluminescence intensity on AlN layer thickness is studied using an exponential model to describe the tunneling probability from the near-surface quantum well to the GaAssurface.Peer reviewe

Stress distribution in GaN nanopillars using confocal Raman mapping technique

In this Letter, high-resolution confocal Raman mapping of stress distribution in etched and re-grown GaN nanopillar structures is investigated. Results of the E2(high) phonon line mapping of the top surfaces of individual nanopillars reveal differences in stress between both the center and edge of the nanopillar top surfaces and between the etched and re-grown GaN nanopillar structures. In-plane biaxial compressive stress with the values of 0.36–0.42 GPa and 0.49–0.54 GPa is observed at the center of etched and re-grown GaN nanopillars, respectively. The in-plane biaxial compressive stress decreases from center to edge in re-grown GaN nanopillar due to the tilted facets. Also, the A1(LO) phonon frequency increases from center to edges, or tilted facets, due to the tilt of the c-axis of re-grown GaN nanopillar.Peer reviewe

Catalyst-free growth of In(As)P nanowires on silicon

The catalyst-free metal organic vapor phase epitaxialgrowth of In(As)P nanowires on silicon substrates is investigated using in situ deposited In droplets as seeds for nanowiregrowth. The thin substrate native oxide is found to play a crucial role in the nanowire formation. The structure of the nanowires is characterized by photoluminescence and electron microscopy measurements. The crystal structure of the InPnanowires is wurtzite with its c axis perpendicular to the nanowire axis. Adding arsenic precursor to the gas phase during growth results in a bimodal photoluminescence spectrum exhibiting peak at the InAsP and InP band gap energies.Peer reviewe