摘要:

Interfaces of pseudomorphic (100) ZnSe/GaAs heterostructures grown by molecular beam epitaxy have been studied by transmission electron microscopy. The observation of three different heterostructures suggests the existence of a transition structure at the ZnSe/GaAs interfaces which have formed on As‐deficient GaAs surfaces. The transition structure appears as a bright line in dark field images of the 200 reflection, while it becomes a dark line in dark field images of the 400 reflection. These observations are explained by assuming the existence of an interface layer which has a zinc blende type structure having vacancies in one of the face centered cubic sublattices.

ISSN:0003-6951    

DOI:10.1063/1.103662

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Magnetotransport measurements have been performed in thin cobalt disilicide films epitaxially grown on Si(111) wafers. Films of thickness between 4.0 and 20.0 nm were studied in order to ascertain the important electron scattering rates. A temperature independent contribution to the phase breaking scattering rate was determined and attributed to spin–spin scattering of the conduction electrons which increases as the film thickness is decreased. The origin of this scattering and its importance to the low‐temperature electron transport are discussed.

ISSN:0003-6951    

DOI:10.1063/1.103663

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is shown for the first time that the recently developed calorimetric absorption spectroscopy (CAS) is most fruitfully applicable as a direct measure of nonradiative decay of excitonic systems even concerning their fine structure properties if experiments are performed in the mK range achieved in a3He/4He‐dilution refrigerator. CAS gives hints on different scattering and relaxation processes of longitudinalALand tripletAFexcitons in CdS, and directly evidences nonradiative decay ratios of different bound‐exciton complexes. Even TA‐phonon‐assisted recombination of such systems leads to well measurable CAS signal enhancement.

ISSN:0003-6951    

DOI:10.1063/1.103664

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Direct measurements of the surface recombination velocity (SRV) on etched CdS(112¯0), CdSe(112¯0) and at their interfaces with various metal ions and metals (deposited by electrolyte aqueous solutions andinsituthermal evaporation, respectively) have been performed using ultrafast time‐resolved photoluminescence (PL). Correlations with interface states types and energy positions have been found based on surface photovoltage spectroscopy (SPS). The results show that the original semiconductor SRV is retained, and in some cases even decreases, when these surfaces are covered with metals, which tend to react with the semiconductor’s anion, such as Al, Ti, and Zn. On the other hand, the SRV increases sharply as a function of unreactive metals coverage, such as Cu, Au, etc. The PL results are explained in terms of metal‐induced recombination centers at the semiconductor interface, which are introduced or eliminated as observed by SPS.

ISSN:0003-6951    

DOI:10.1063/1.103665

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Si planar‐doped AlInAs layers grown by metalorganic chemical vapor deposition (MOCVD) showed an excellent uniformity in doping concentration. It was caused by the saturation of the doping concentration in the high doping region. Applying this planar doping to the AlInAs/GaInAs heterointerface field‐effect transistor (HIFET), the variation of the threshold voltage (Vth) due to unevenness of distribution of doping concentration was reduced to values below 50 mV over a 2‐in.‐diam wafer.

ISSN:0003-6951    

DOI:10.1063/1.103666

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Current‐voltage characteristics of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy with nonuniform doping in the base region have been studied. Experimental measurements indicate that an optimization of the base doping leads to substantial improvement in the current gain and related properties. Unequal variations of the band‐gap narrowing effect and Fermi–Dirac statistics effect seem to underlie this improvement. It is found that, in general, the higher the nonuniformity of the base doping, the lower is the offset voltage of the HBT.

ISSN:0003-6951    

DOI:10.1063/1.103667

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Optical characteristics of a new, weakly strained wide‐gap II‐VI quantum well have been studied with emphasis on the confined exciton states. Strong luminescence efficiency in the blue is observed with spectra showing only weak alloy disorder effects. Magneto‐optical studies yield a measurement for the band offsets in a model which properly includes exciton effects.

ISSN:0003-6951    

DOI:10.1063/1.104104

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The conduction‐band discontinuities and interface charge densities of severaln‐Nisotype InxGa1−xAs/InP (x&bartil;0.53) heterojunctions with lattice mismatches (&Dgr;a/a) ranging from +0.26 to −0.24% were measured using capacitance‐voltage techniques. To facilitate these measurements, organic‐on‐inorganic contact barrier diodes were used. Extremely low interface charge densities (<1×1010cm−2) are obtained for all the samples, which are approximately one order of magnitude lower than previously reported values for these heterojunctions. We find that the interface charge density is independent of the magnitude of lattice mismatch and temperature. All the samples show a clear peak‐and‐notch in their apparent free‐carrier concentration profiles at temperatures as low as 83 K. This is in contrast to results reported previously where the notch is observed to disappear at low temperature. The measured heterojunction conduction‐band discontinuity is also found to be temperature independent, with a value of 0.22±0.02 eV.

ISSN:0003-6951    

DOI:10.1063/1.103668

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effect of room‐temperature electron beam irradiation on the Al‐Ga interdiffusion at GaAs/AlGaAs quantum well heterointerfaces is investigated with low‐temperature cathodoluminescence spectroscopy. The interdiffusion is enhanced by defects generated through an irradiation with a 400 keV electron beam. After room‐temperature irradiation with a dose of ∼1.5×1017–2.5×1017/cm2and subsequent rapid thermal annealing at 900 °C for 1 min, an interdiffusion length of 3–5 A˚ is obtained. The electron beam induced damage tends to saturate with increasing irradiation dose, and the formation of defect cluster at high dose limits the defect introduction and, thus, the interdiffusion at the interface.

ISSN:0003-6951    

DOI:10.1063/1.103669

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The dependence of the intersubband transitions on pressure in strained In0.15Ga0.85As/GaAs multiple quantum wells has been studied in two samples with well widths of 8 and 15 nm, respectively, with photomodulated transmission spectroscopy by using a diamond anvil cell. The pressure coefficients of the energies for the intersubband transitions were found to depend significantly on the well widths and to be smaller than that of the band gap of constituents in bulk form. These results suggested that the critical thickness for strained In0.15Ga0.85As/GaAs layer should be smaller than 15 nm.

ISSN:0003-6951    

DOI:10.1063/1.103670

出版商:AIP    

年代:1990

数据来源: AIP