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Photoluminescence Investigation of Two-Dimensional Electron Gas in an Undoped AlxGa1-xN／GaN Heterostructure

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Chinese Physics Letters 2005年第8期22卷 2096-2099页

作者：韩修训吴洁君李杰民丛光伟刘祥林朱勤生王占国 keylaboratoryofsemiconductormaterialsscience InstituteofSemiconductorsChineseAcademyofSciencesPOBox912Beijing100083

Low-temperature photoluminescence measurement is performed on an undoped AlxGa1−xN/GaN heterostructure. Temperature-dependent Hall mobility confirms the formation of two-dimensional electron gas (2DEG) near the heterointerface. A weak photoluminescence (PL) peak with the energy of ~79meV lower than the free exciton (FE) emission of bulk GaN is related to the radiative recombination between electrons confined in the triangular well and the holes near the flat-band region of GaN. Its identification is supported by the solution of coupled one-dimensional Poisson and Schrödinger equations. When the temperature increases, the red shift of the 2DEG related emission peak is slower than that of the FE peak. The enhanced screening effect coming from the increasing 2DEG concentration and the varying electron distribution at two lowest subbands as a function of temperature account for such behaviour.

关键词： DEG TMA MOCVD

Modulation Spectroscopy of GaAs Covered by InAs Quantum Dots

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Chinese Physics Letters 2002年第7期19卷 1010-1012页

作者：金鹏李乙钢等 keylaboratoryofsemiconductormaterialsscience InstituteofSemiconductorsChineseAcademyofSciencesPOBox912Beijing100083 DepartmentofPhysics NankaiUniversityTianjin300071

Contactless electroreflectance has been employed at room temperature to study the Fermi level pinning at undoped-n+ GaAs surfaces covered by 1.6 and 1.8 monolayer (ML) InAs quantum dots (QDs). It is shown that the 1.8 ML InAs QD moves the Fermi level at GaAs surface to the valence band maximum by about 70 meV compared to bare GaAs, whereas 1.6 ML InAs on GaAs does not modify the Fermi level. It is confirmed that the modification of the 1.8 ML InAs deposition on the Fermi level at GaAs surface is due to the QDs, which are surrounded by some oxidized InAs facets, rather than the wetting layer.

关键词： Indium arsenide

Nanocavity Shrinkage and Preferential Amorphization during Irradiation in Silicon

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Chinese Physics Letters 2005年第3期22卷 657-660页

作者：朱贤方王占国 LaboratoryofLow-DimensionalNanostructures DepartmentofPhysicsandNanomaterialsCenterXiamenUniversityXiamen361005 keylaboratoryofsemiconductormaterialsscience InstituteofSemiconductorsChineseAcademyofSciencesPOBox912Beijing100083

We model the recent experimental results and demonstrate that the internal shrinkage of nanocavities in silicon is intrinsically associated with preferential amorphization as induced by self-ion irradiation. The results reveal novel thermodynamic nonequilibrium properties of such an open-volume nanostructure in condensed matter and also of covalently bound amorphous materials both at nanosize scale and during ultrafast interaction with energetic beam.

关键词： Nanocavity Shrinkage Preferential Amorphization during Irradiation in Silicon

Evidence of Ultrafast Energy Exchange-Induced Soft＇ Mode of Phonons and Lattice Instability： a Nanotime Effect

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Chinese Physics Letters 2005年第3期22卷 737-740页

With a series of supportive experimental phenomena as induced by ion beam bombardment, energetic beam-induced athermal activation process in Si is demonstrated. This is correlated with phenomena induced by ultrafast energy exchange in condensed matter in general. A critical modelling is presented on the above process and a universal concept: the ultrafast energy exchange-induced soft mode of phonons and the lattice instability in condensed matter are proposed.

关键词： Ultrafast Energy Exchange-Induced Soft Mode Phonons Lattice Instability Nanotime Effect

Rapid Thermal Annealing Effects on Structural and Optical Properties of Self-Assembled InAs／GaAs Quantum Dots Capped by InAIAs／InGaAs Layers

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Chinese Physics Letters 2005年第4期22卷 967-970页

作者：吕威黎大兵张子旸李超荣张泽徐波王占国 BeijingLaboratoryofElectronMicroscopy InstituteofPhysicsandCenterforCondensed~latterPhysicsChineseAcademyofSciencesPOBox603Beijing100080 keylaboratoryofsemiconductormaterialsscience InstituteofSemiconductorsChineseAcademyofSciencesPOBox912Beijing100083 BeijingUniversityofTechnology Beijing100022

Effects of rapid thermal annealing on the optical and structural properties of self-assembled InAs/GaAs quantum dots capped by the InAlAs/InGaAs combination layers are studied by photoluminescence and transmission electron microscopy. The photoluminescence measurement shows that the photoluminescence peak of the sample after 850 degrees C rapid thermal annealing is blue shifted with 370meV and the excitation peak intensity increases by a factor of about 2.7 after the rapid thermal annealing, which indicates that the InAs quantum dots have experienced an abnormal transformation during the annealing. The transmission electron microscopy shows that the quantum dots disappear and a new InAlGaAs single quantum well structure forms after the rapid thermal annealing treatment. The transformation mechanism is discussed. These abnormal optical properties are attributed to the structural transformation of these quantum dots into a single quantum well.

关键词：热退火效应结构性质光学性质自适应量子点铟镓砷多层薄膜

Realization of Low Threshold of InGaAs／InA1As Quantum Cascade Laser

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Chinese Physics Letters 2003年第9期20卷 1478-1481页

作者：刘峰奇金鹏王占国李成明 Towhomcorrespondenceshouldbeaddressed keylaboratoryofsemiconductormaterialsscience InstituteofSemiconductorsChineseAcademyofSciencesPOBox912Beijing100083

Effect of Misfit Dislocation Originated from Strained Layer on Photoluminescence Properties of InxGa1-xN／GaN Multiple Quantum Wells

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Chinese Physics Letters 2005年第4期22卷 971-974页

作者：吕威黎大兵李超荣陈岗张泽 DepartmentofMaterialsScience CollegeofMaterialsScienceandEngineeringJilinUniversityChangchun130012 keylaboratoryofsemiconductormaterialsscience InstituteofSemiconductorsChineseAcademyofSciencesPOBox912Beijing100083 BeijingLaboratoryofElectronMicroscopy InstituteofPhysicsChineseAcademyofSciencesPOBox603Beijing100080 BeijingUniversityofTechnology Beijing100022

InxGa1−xN/GaN multiple quantum well (MQW) samples with strain-layer thickness larger/less than the critical one are investigated by temperature-dependent photoluminescence and transmission electron microscopy, and double crystal x-ray diffraction. For the sample with the strained-layer thickness greater than the critical thickness, we observe a high density of threading dislocations generated at the MQW layers and extended to the cap layer. These dislocations result from relaxation of the strain layer when its thickness is beyond the critical thickness. For the sample with the strained-layer thickness greater than the critical thickness, temperature-dependent photoluminescence measurements give evidence that dislocations generated from the MQW layers due to strain relaxation are main reason of the poor photoluminescence property, and the dominating status change of the main peak with increasing temperature is attributed to the change of the radiative recombination from the areas including dislocations to the ones excluding dislocations.

关键词：错配断层有机效应光激发光加固层氮化镓合金量子井