摘要:

We have observed dips with negative values in the curve of the differential conductance of the base versus the base‐emitter voltagedIB/dVBEat 77 K in GaInAs/InP hot‐electron transistors grown by organometallic vapor phase epitaxy. The efficiency of the hot‐electron transmission across the 40‐nm‐thick base was more than 0.99. In comparison with a theoretical model considering that observed dips should have been caused by the resonant states in the base well, the phase relaxation time of the hot electron is estimated to be in the order of 0.1 ps or longer.

ISSN:0003-6951    

DOI:10.1063/1.103956

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Reflection high‐energy electron diffraction intensity dynamic behavior was examined on GaAs, AlAs, and Al0.5Ga0.5As layers using As4and/or As2flux to establish optimum growth conditions for heterointerfaces. Results show that As4is preferable for the growth of AlAs and Al0.5Ga0.5As, while As2is better for GaAs. This finding is explained on the basis of the expected dynamic surface kinetic processes. Low‐temperature photoluminescence line width of a quantum well (20 monolayer GaAs well/100 monolayer Al0.5Ga0.5As barriers) grown under the optimized growth condition is 4.5 meV.

ISSN:0003-6951    

DOI:10.1063/1.103930

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Direct evidence for interplanar relaxation in islands at the initial stages of strained epitaxy is presented using molecular beam epitaxically deposited In0.5Ga0.5As on GaAs(100). Concomitant existence of atomic displacements in the substrates to unexpectedly large depths of ∼150 A˚ is found. In incoherent islands, defects are found to be introduced symmetrically near the island edges.

ISSN:0003-6951    

DOI:10.1063/1.103914

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A recently developed As2S3chemical treatment was used to passivate the perimeters of self‐aligned heterojunction bipolar transistors (HBTs). The As2S3chemical treatment significantly lowered the base current resulting in a two order of magnitude reduction in the collector current density at which dc current gain was observed (&bgr;=1). No degradation with time has been observed in the electrical characteristics of the chemically treated HBTs. This absence of degradation is attributed to the impermeability to oxygen of the As2S3glass which coats the perimeter of the HBT after chemical treatment.

ISSN:0003-6951    

DOI:10.1063/1.104114

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report the first room‐temperature observation of Wannier–Stark localization in a strained InGaAs/GaAs superlattice. The localization effects are in close agreement to theory. At low electric fields, the room‐temperature absorption data show a small Wannier exciton peak at the lower edge of the miniband, and a more prominentM1exciton at higher energy. At higher fields, the miniband localizes to a single quantum well exciton with accompanying +1 and −1 transitions. At even higher fields the initial blue shift of the Wannier exciton changes to a Stark effect red shift with a &Dgr;&agr;/&agr; of about 3.

ISSN:0003-6951    

DOI:10.1063/1.103915

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Franz–Keldysh oscillations from GaAs and AlGaAs structures have been studied and we find that the electric field obtained from the oscillations is in agreement with that derived from electrostatic calculations. Our results show that illumination from pump and probe beams in a normal photoreflectance experiment can significantly affect the measurement and thus erroneously lead to a reduced value of the electric field. The Fermi level on the bare surface of AlGaAs with different Al mole fraction has also been determined.

ISSN:0003-6951    

DOI:10.1063/1.103916

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The use of a liquid organic source forn‐type doping in hydrogenated amorphous silicon (a‐Si:H) is described. Tertiarybutylphosphine (TBP) vapor is added to silane in a rf glow discharge process to produce dopeda‐Si:H thin films. Impurity levels from parts per million to about 1% phosphorus have been incorporated into the film with this method. Measurements of dark conductivity, photoconductivity, conductivity activation energy, electron spin resonance, and sub‐gap optical absorption of the TBP‐doped films are compared to those published for films doped with phosphine.

ISSN:0003-6951    

DOI:10.1063/1.103917

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Expressions are presented for the rate of strain relaxation, misfit dislocation nucleation, and propagation in strained Si1−xGex/(100)Si heterostructures. Independent measurements of misfit dislocation nucleation and 60° typea/2 ⟨110⟩ dislocation glide velocity in the temperature range 450–1000 °C have led to a model which characterizes the kinetics of strain relaxation for 0<x<0.25. The generalized force or effective stress &tgr;eff, which drives strain relaxation, is defined for an arbitrary strain profile and strained‐layer geometry. New experimental data for misfit dislocation glide velocity (Vin cm s−1) have been fitted to a semi‐empirical relation found to be appropriate for all Si1−xGex/(100)Si heterostructures,V=(4±2)⋅1013(&tgr;eff/&mgr;)2 exp−[(2.25±0.05)/kT]. An analogous expression for the nucleation rate of new misfit dislocation segments was determined from experimental data,dN(t)/dt=BN0(&tgr;eff/&mgr;)2.5 exp−[2.5±0.2)/kT], whereN0is the density of heterogeneous nuclei andBis a material constant ∼1018s−1for Si1−xGex. These expressions are combined in a kinetic model which is then used to predict the rate of strain relaxation in Si1−xGex/Si heterostructures.

ISSN:0003-6951    

DOI:10.1063/1.103918

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A novel approach to producingp‐type ZnSe epitaxial layers is reported which involves nitrogen atom beam doping during molecular beam epitaxial growth. Net acceptor concentrations as large as 3.4×1017cm−3have been measured in nitrogen atom beam doped ZnSe/GaAs heteroepitaxial layers which represents the highest acceptor concentration reported to date for ZnSe:N epitaxial material grown by molecular beam epitaxy. In addition, light‐emitting diodes based on ZnSe:N/ZnSe:Cl,p‐nhomojunctions have been found to exhibit dominant electroluminescence in the blue region of the visible spectrum at room temperature.

ISSN:0003-6951    

DOI:10.1063/1.103919

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report the realization of a novel superlattice which contains a high mobility (&bartil; 1.1×105cm2/V s at 4 K)degenerateelectron system. The structure consists of a wide, undoped AlxGa1−xAs well bounded by undoped (spacer) and doped layers of AlyGa1−yAs (y≳x) on both sides. The alloy composition in the well (x) is graded in such a way as to result in a parabolic potential with an additional sinusoidal modulation superimposed on it. Once transferred into this well, the electrons screen the parabolic potential and an electron system with a modulated charge density is obtained. We present self‐consistent quantum mechanical calculations of the electronic system, and report our characterization of the structure by secondary‐ion mass spectrometry and magnetotransport measurements.

ISSN:0003-6951    

DOI:10.1063/1.103920

出版商:AIP    

年代:1990

数据来源: AIP