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

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

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

Selective growth of InGaAs on nanoscale InP islands

The formation of an InGaAs quantum well on nanoscale InP islands by selective growth using metalorganic vapor phase epitaxy is demonstrated. The structures show intense low‐temperature photoluminescence at 1.35 eV. The blueshift of the emission peak by increasing the excitation intensity suggests that the carriers are three‐dimensionally confined. The insertion of quantum well into the islands allows a better control of the properties of structuresfabricated by the self‐organizing growth, a novel technique to realize nanoscale structures without using any lithographical process steps.Peer reviewe

Experimental investigation towards a periodically pumped single-photon source

Experiments towards a periodically pumped single-photon source are presented. The lateral piezoelectric field of a surface acoustic wave dissociates laser-generated two-dimensional excitons into electrons and holes. These carriers are separated by the wave potential and are transported over macroscopic length scales without recombining. When reaching a stress-induced quantum dot in the quantum well they periodically populate the zero-dimensional states and recombine, emitting single photons periodically in time according to the surface acoustic-wave frequency. We have successfully reduced the number of pumped quantum dots down to 100 and have detected a strong blinking photoluminescence signal. By further reducing the number of quantum dots down to 1 a periodically pumped single photon source could be realized.Peer reviewe

In situ determination of nitrogen content in InGaAsN quantum wells

The growth of InGaAsN/GaAs multiple quantum well structures by metal-organic vapor phase epitaxy is monitored by in situ reflectometry. The nitrogen incorporation is found to depend superlinearly on the precursor flow and a threshold value for the flow is observed. By in situmeasurements of the InGaAsN quantum well samples with a fixed indium content, the change in the reflectance during the quantum wellgrowth is found to be linearly dependent on the quantum well nitrogen content. A model to determine the nitrogen content already during the growth is developed. Moreover, the field of application of in situ reflectance monitoring is extended from thick layers to thin layers, including quantum wells.Peer reviewe