摘要:

We report strong transmission electron microscope (TEM) contrast betweenp‐,i‐, andn‐doped InP layers in semiconductor laser diodes. For doping concentrations ∼1018cm−3, contrast levels on the order 30% are observed betweenp‐ andn‐type layers. A critical feature of these experiments is that the samples imaged in the TEM are relatively perfect, plane‐parallel sided membranes fabricated with a focused ion beam. This technique offers the ability to detect and map doping variations with nm‐scale resolution, simultaneously with the other compositional and defect information inherent to TEM. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114206

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Quantitative dopant profile measurements are performed on a nanometer scale by scanning capacitance microscopy (SCM). An atomic force microscope is used to position a nanometer scale tip at a semiconductor surface, and local capacitance change is measured as a function of sample bias. A new feedback method has been demonstrated in which the magnitude of the ac bias voltage applied to the sample is adjusted to maintain a constant capacitance change as the tip is scanned across the sample surface. A quasi‐1D model is used to extract dopant density profiles from the SCM measurements. The inverted SCM dopant profiles are compared with profiles obtained by process simulation and secondary ion mass spectroscopy measurement. Good agreement was found between the SCM measured profile and the lateral profile predicted by SUPREM 4 over the concentration range from 1017to 1020cm−3. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114207

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A lattice‐matched In0.53Al0.22Ga0.25As/InP heterojunction bipolar transistor has been fabricated by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD). No potential spike due to zero conduction band discontinuity at the emitter‐base heterojunction is obtained. Meanwhile, the larger valence discontinuity (&Dgr;EV=460 meV) than AlGaAs/GaAs and InGaAs/InP systems provides this structure with a better hole confinement. An offset voltage as low as 50 mV along with a current gain of 85 is achieved. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114208

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoconduction in heterogeneous thin films consisting of a porous nanocrystalline TiO2matrix and internally adsorbed quantum size PbS clusters is reported. The TiO2serves to establish electrical contact to the PbS clusters, and the PbS cluster size is chosen so that photogenerated excess electrons are directly injected from the PbS to the TiO2. The films exhibit strong photoconductance in the visible region, indicating photoelectric sensitization of the TiO2by the PbS clusters. Comparison of the absorption and photocurrent spectra shows that only PbS clusters of sizes smaller than ∼25 A˚ contribute to the sensitization. For larger clusters the band alignment at the TiO2/PbS interface appears to be unfavorable for carrier transfer. Further improvement in the photoresponse will have to involve optimization of the transport properties in the nanocrystalline TiO2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114209

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The surface chemistry of triethylaluminum, triethylgallium, triethylindium, and triethylantimony was studied on GaAs(100) using thermal desorption spectroscopy, static secondary ion mass spectroscopy, and x‐ray photoelectron spectroscopy. Ethylene, the major hydrocarbon reaction product, desorbs from the GaAs(100) surface during thermal desorption spectroscopy experiments at 565 K for all four molecules. This indicates an identical rate limiting step for the elimination of ethyl groups from the surface following adsorption of these molecules. We propose that ethyl groups migrate to Ga sites and then undergo reaction at these sites. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114210

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Diffusion of ion implanted Be in AlxGa1−xAs was studied as a function of Al concentration and annealing temperature and was compared to diffusion in GaAs. The behavior of Be in AlxGa1−xAs is similar to that in GaAs, even showing the anomalous behavior of increasing redistribution with decreasing temperature. The diffusivity of Be appears to increase with Al content which may be due to increasing bonding strength of matrix atoms with the addition of Al, preventing the easy transferral of Be from interstitial to substitutional sites. The oversaturation of Be interstitials may also explain the persistence of anomalous diffusion behavior in AlxGa1−xAs with respect to anneal temperature. This is discussed in terms of the substitutional‐interstitial diffusion mechanism, the relative amount of interstitial and substitutional Be, and the relative difficulty of moving from an interstitial to a substitutional site. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114211

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence imaging was used to study photodegradation in CdZnSe quantum wells, important to II‐VI based blue‐green light emitter technology. The observed degradation microstructure evolves similarly to features observed during CdZnSe based LED and laser operation. Degradation is shown to emanate from pre‐existing defects to form dark line defects along the ⟨100⟩ directions. We report an observation of a mobile defect in II‐VI materials that is the precursor to the ⟨100⟩ dark line defects.

ISSN:0003-6951    

DOI:10.1063/1.114212

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have prepared small InP islands which are embedded in In0.485Ga0.515P grown on a (100) GaAs substrate by solid‐source molecular beam epitaxy. The InP islands form due to the 3.7% lattice mismatch between In0.485Ga0.515P and InP. Atomic force microscopy measurements show that the island size is typically ∼50 nm in diameter and ∼5 nm in height for nominally two monolayers of InP deposited on In0.485Ga0.515P. The energy of the photoluminescence (PL) peak shifts from 1.85 to 1.53 eV as the nominal InP thickness increases from 2 to 10 monolayers. A minimum PL linewidth of 21.6 meV and the maximum intensity of the PL originating from the InP islands is observed for 7.3 monolayers InP. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114213

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Heterostructures with biaxially compressed InAsSb are being considered as active regions for midwave infrared diode lasers. Quantum wells of biaxially compressed InAs1−xSbx(x≊0.09) in unstrained InAs were characterized using magnetophotoluminescence. The quantum size shift of the photoluminescence for a series of quantum wells produced an estimate of the conduction band offset. In magnetic field studies, the holes in the strained quantum wells exhibited a decrease in effective mass, approaching that of the electrons. A type I band offset was observed for these InAsSb/InAs heterostructures. Throughout this study, magnetoexcitonic behavior is observed; our analysis indicates that the exciton binding energy increases with quantum confinement. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114214

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using TMGa and TEGa simultaneously for the metalorganic molecular beam epitaxy growth of GaAs, interactions between the precursors have been observed. Whereas the resulting growth rate is unaffected, the obtained carrier concentrations reveal deviations up to 85% from the superpositioned values. Separate and common injection of both group III alkyls have been investigated. From these, interactions within the common group III injector, if they take place at all, are found to be negligible compared to interactions on the surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114215

出版商:AIP    

年代:1995

数据来源: AIP