摘要:

Determination of alloy composition during epitaxial growth of GexSi1−xalloys has been demonstrated using reflection‐electron energy loss spectroscopy (REELS) at reflection high‐energy electron diffraction (RHEED) energies. Measurements of inelastic scattering intensities from SiK(1840 eV) and GeL2,3(1217 eV) core losses were performed using a conventional RHEED gun together with an electron energy loss spectrometer in a molecular beam epitaxy system. Comparison ofexsitucomposition measurements by Rutherford backscattering and energy dispersive x‐ray spectroscopy in a transmission electron microscope indicate excellent agreement with composition determination by REELS, demonstrating the capability of REELS as a quantitativeinsituanalysis technique. Application of REELS to other semiconductors is discussed and initial results for III–V and II–VI semiconductor alloys (GaAs, CdTe, and ZnTe) are also presented.

ISSN:1071-1023    

DOI:10.1116/1.586443

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We have compared the growth front smoothness of strained layers grown by migration‐enhanced epitaxy and molecular‐beam epitaxy by looking at the oscillation maxima of reflection high‐energy electron diffraction intensities. We find that for growth of InxGa1−xAs on GaAs withxless than ∼0.15, migration‐enhanced epitaxy improves the surface quality, while for larger amounts of mismatch (x≳0.15) the surface profile during migration enhanced epitaxy growth is worse than during conventional As‐stabilized molecular‐beam epitaxial growth. Results of Hall mobility, photoluminescence measurements, and modulation‐doped transistor characteristics are consistent with the diffraction intensity studies.

ISSN:1071-1023    

DOI:10.1116/1.586444

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We have analyzed data obtained from double‐crystal x‐ray rocking curve measurements to determine the lattice constants, strain relaxation, thickness, and critical thickness of a thin InxGa1−xAs layer embedded in GaAs. The use of a very wide x‐ray scan angle (∼2.0°) allows the simultaneous determination of buried layer thickness and strain with greater accuracy. The critical thicknesses so obtained for buried InGaAs layers are smaller than that predicted by the energy balance model and larger than that predicted by the force balance model.

ISSN:1071-1023    

DOI:10.1116/1.586445

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A series of (InAs)m(GaAs)nshort‐period superlattice layers withm=0.87, 1, 1.15, or 2 andn=3, 5, 6, 7, or 8 were grown about 0.3 μm thick on GaAs substrates by migration enhanced epitaxy. Changes in reflection high‐energy electron diffraction (RHEED) patterns indicate that the surface is roughened by InAs layers, but becomes smooth by deposition of GaAs layers. Large or nonintegralminduces more surface roughening, while largenis more effective in smoothing. For most samples, RHEED patterns became spotty beyond some total superlattice thickness depending onmandn. The positions and full width at half‐maximums of the zeroth‐order superlattice peaks of x‐ray diffraction are correlated to the observations in RHEED. We conclude that strain‐induced interface roughening is one of the major causes to short‐period superlattice imperfections, and that nonintegral InAs layers significantly affect the roughening.

ISSN:1071-1023    

DOI:10.1116/1.586446

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We report the successful growth of high‐quality molecular‐beam epitaxy (MBE) GaAs, AlGaAs, AlGaAs/GaAs modulation‐doped heterostructures, GaAs/InGaAs/GaAs quantum well, and AlGaAs/InGaAs multiple quantum wells (NQW) on GaAs (111)B substrates. Modulation‐doped heterostructures show a 77‐K mobility of 145 500 cm2/V s with a sheet density of 5.0×1011cm−2. Photoluminescence of (111)B GaAs indicates a lower carbon incorporation than achieved on (100) substrates. The high material quality obtainable at low growth temperatures for (111)B growth will be advantageous for laser diode and heterostructure field‐effect transistor applications. AlGaAs/InGaAs MQW on (111)B are comparable in the photoluminescence linewidths to those on (100) GaAs.

ISSN:1071-1023    

DOI:10.1116/1.586113

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Si‐dopedn‐type GaAs and Be‐dopedp‐type GaAs have been grown on (111)B oriented GaAs substrates using the migration‐enhanced epitaxy (MEE) technique, in which arsenic and gallium are deposited separately. The mobilities and carrier densities have been compared with GaAs grown by MEE and conventional epitaxy on GaAs (100) substrates. Under migration enhanced conditions, the range of substrate temperatures and arsenic fluxes to obtain smooth surfaces and good mobilities is wider than for conventional molecular‐beam epitaxy, for both substrate orientations. High‐quality doped GaAs material was obtained at substrate temperature as low as 400–450 °C on (111)B substrates.

ISSN:1071-1023    

DOI:10.1116/1.586114

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

GaAs/AlGaAs quantum wells have been successfully grown over 10 nm thick epitaxial CoAl layers with molecular‐beam epitaxy and characterized with transmission electron microscopy (TEM) and photoluminescence. Cross‐sectional TEMs of the structures showed well‐defined GaAs and AlGaAs epitaxial layers, and photoluminescence spectra taken at 77 K showed reasonably bright and narrow quantum‐well (QW) exciton peaks compared to structures grown over GaAs. This preliminary work indicates the feasibility of growing epitaxial quantum wells over a CoAl layer. The ability to grow low‐defect buried epitaxial metals together with InGaAs/AlGaAs or GaAs/AlGaAs QWs would enable the fabrication of a variety of unique electro‐optical devices incorporating buried optical mirrors, Schottky barriers, and/or ohmic electrical contacts.

ISSN:1071-1023    

DOI:10.1116/1.586115

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We report on the realization of high quality single quantum wells (SQWs) in the highly strained AlxGa1−xAs/In0.26Ga0.74As/AlzGa1−zAs system with 0≤(x,z)≤1.0. Photoluminescence (PL) linewidths of 5.5±0.4 meV for 0.30≤(xandz)≤0.70 have been achieved. Use of both alloys and short period multiple layer structures as the well and/or barrier layers has been examined. The silicon nitride encapsulation as well as rapid thermal annealing (RTA) induced changes in the PL properties of the as‐grown SQW structures have been examined. Deposition of the nitride is found to induce a blue shift in the exciton peak. RTA induces a further blue shift, though not as large as that induced by RTA of unencapsulated (i.e., as‐grown) structures. The RTA induced changes indicate interdiffusion of the group III atoms at the GaAs/InGaAs and InGaAs/AlGaAs interfaces.

ISSN:1071-1023    

DOI:10.1116/1.586117

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The interfacial properties of a series of GaAs/AlAs quantum wells (QWs) grown by molecular‐beam epitaxy is examined using photoluminescence (PL). These high‐quality QWs show splittings in the free exciton peaks, which indicate that large scale island structures exist at the interfaces. By changing the growth temperature we are able to shift the absolute energies of the excitons while keeping the same PL linewidths and lineshapes. Since the absolute energies of the excitons depend only on the GaAs and AlAs material parameters, we conclude that we are able to modify the small scale structure of the interfaces within the large scale islands by changing the growth temperature.

ISSN:1071-1023    

DOI:10.1116/1.586119

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The flux of Ga and Al from molecular‐beam epitaxy effusion cells has a significant noise component. The magnitude of this noise has been measured to be as large as 8% of the average flux and the frequency distribution of this noise was centered near 0.1 Hz. The magnitude of the flux noise was found to depend on the amount of material in the cell, the element in the cell, and the thermal gradient in the cell. A correlation between the flux noise and the oval defect densities in GaAs grown with these effusion cells is observed. The defect densities range from 1000 cm−2for a Varian 16 cc Ga cell to a low of less than 50 cm−2for an EPI 60 cc cell. While no complete theory exists, there are two potential sources of flux noise: hydrodynamic instabilities of the melt and source ‘‘spitting.’’

ISSN:1071-1023    

DOI:10.1116/1.586120

出版商:American Vacuum Society    

年代:1992

数据来源: AIP