摘要:

A new versatile procedure combining conventional lithography and focused ion beam coupled to scanning electron microscopy to micromachine high‐quality cross‐sectional transmission electron microscopy (TEM) samples is proposed. Electron transparent areas are generated with a high degree of localization, within 0.1 μm, over distances of several millimeters in GaAs/GaAlAs heterostructures. TEM observations demonstrate that no defects are introduced during the thinning process and different conditions of illumination are achievable.

ISSN:0734-211X    

DOI:10.1116/1.586840

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Epitaxial growth of InP and GaAs (AlGaAs) in narrow (∼1 μm wide) trenches and around mesas formed by highly anisotropic dry etching was performed by low‐pressure (30 Torr) organometallic vapor phase epitaxy (OMVPE) and metalorganic molecular beam epitaxy (MOMBE). For the [110] oriented trenches and mesas, MOMBE produced highly selective regrowth of both materials under normal growth conditions. By contrast, it was necessary to add CCl4to the growth chemistry in OMVPE to eliminate deposition on the SiNxmask during growth in trenches and around mesas. Due to growth rate enhancement near the edge of the masked regions, acceptable control of the growth thickness in OMVPE could only be obtained for the case of mesas, but not for narrow trenches.

ISSN:0734-211X    

DOI:10.1116/1.586796

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The influence of substrate temperature on the growth of InGaAs layers on (111)B GaAs, has been studied. Photoluminescence (PL) spectra obtained from GaAs/InGaAs single quantum well structures show strong dependence on InGaAs growth temperature. As the growth temperature increases, PL peaks shift to a higher energy, which is attributed to reevaporation of indium from the InGaAs layer during the growth at higher substrate temperatures. An activation energy of 3.1±0.2 eV for indium desorption from the (111)B GaAs substrate was obtained. InGaAs layers grown below 530 °C, where reflection high‐energy electron diffraction shows (2×2) reconstruction, exhibit a wider PL linewidth than those grown above 530 °C. The optimum temperature for growth of InGaAs on (111)B GaAs substrates is the lowest possible temperature where one can maintain a (√19×√19)R23.4 reconstruction; this varies with the group V/III beam equivalent pressure ratio.

ISSN:0734-211X    

DOI:10.1116/1.586797

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Fabrication of submicron high electron mobility transistors (HEMTs) involves dry etch removal of GaAs from an underlying AlGaAs or InGaAs stop layer. The etch selectivity is achieved by formation of AlF3on AlGaAs, or InCl3and InF3on InGaAs, which must be removed before processing can proceed. Wet chemical cleaning has difficulty in such a situation because of surface tension effects. We have investigated use of electron cyclotron resonance (ECR) H2or Ar discharges, or hexafluoroacetylacetone (HFAC) vapor, forinsitudry etch cleaning of HEMTs exposed to low‐bias BCl3/SF6discharges. The HFAC vapor can remove most of the remnant fluorine, but is effective only when the sample is heated above ∼250 °C. This relatively high temperature is not compatible withinsitucleaning of the etched device. Low‐bias (−75 V) sputter cleaning with an Ar discharge removes all remnant Cl and ∼40% of the F, but direct‐current biases above −125 V are required for complete cleaning, and this ion bombardment can lead to damage in the HEMT. ECR H2discharge exposure is effective in removing all Cl‐ and F‐related residues in a short period (∼5 min) with low direct‐current biases (−25 V) on the sample.

ISSN:0734-211X    

DOI:10.1116/1.586798

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

A CH4/H2gas mixture has been used for the dry etching of (100) and (111) oriented CdTe epilayers in a barrel reactor. The effects of various process parameters on etch rate and surface morphology were studied with special attention paid to the gas composition and the total chamber pressure as well as the crystallographic orientation of the sample. Clear evidence is found for both isotropic and preferential etching along crystallographic planes depending on the set of etch parameters used.  

ISSN:0734-211X    

DOI:10.1116/1.586799

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

A photochemical method for depth profiling multilayered structures of GaAs and AlGaAs is presented. The process combines surface chlorination reactions using molecular chlorine, desorption of surface chlorides, and single step laser ionization time‐of‐flight mass spectroscopy. Pulsed excimer lasers are used for the desorption and ionization steps. The etch rates approached a monolayer per pulse for both substrates. Prospects for improving the resolution of the process in the lateral and vertical dimensions are discussed.

ISSN:0734-211X    

DOI:10.1116/1.586800

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

InGaAs layers of varying epilayer thickness grown at different temperatures on GaAs substrates by molecular‐beam epitaxy are analyzed by atomic force microscopy. The surface roughness and morphology of InGaAs grown at substrate temperatures ranging from 450 to 530 °C are analyzed as the epilayer thickness is increased from 100 to 800 Å. Over an area of 100 μm2, an abrupt increase in the surface roughness probably indicates an acceleration of surface roughening mechanisms related to the process of strain relaxation. At higher InGaAs thicknesses, surface corrugations were observed. The results indicate that thicker pseudomorphic InGaAs films on GaAs substrates can be grown at lower temperatures. Raman spectroscopy data of strain‐induced shifts in the GaAs‐like mode longitudinal optic phonon indicate that the GaAs has tensile strain along the interface. The strain calculated from the observed frequency shift agrees with the lattice‐mismatch strain given by the elasticity theory.

ISSN:0734-211X    

DOI:10.1116/1.586801

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The effect of substrate temperature during deposition on indium oxide/n‐GaAs(110) interfaces, fabricated by means of reactive evaporation of indium in the presence of ∼1×10−4Torr oxygen onto ultrahigh vacuum cleaved GaAs(110) surfaces, has been studied using Auger electron spectroscopy and electron energy loss spectroscopy. The results show that the indium oxide layer growth at room temperature and at 200 °C follows the Stransky–Krastanov model. However, the low temperature growth is characterized by the presence of In clusters at the interface and only minor surface oxidation of the GaAs substrate takes place. At high substrate temperatures, the interface is fully oxidized and includes both indium and arsenic oxide. The results are discussed in view of our earlier reported measurements of indium oxide/GaAs diodes produced under high and ultrahigh vacuum conditions.

ISSN:0734-211X    

DOI:10.1116/1.586802

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The microstructure and electrical properties of Au/Te/Au/n‐GaAs contacts annealed in the temperature range 360–480 °C, either with or without an insulating capping layer, have been investigated by the combined use of Rutherford backscattering spectrometry, x‐ray diffraction, transmission electron microscopy, and current–voltage characterization. In addition, a thin‐film collector method was applied to measure evaporative losses of As and Te, in view of their high volatility during heat treatment. The results give evidence that the thermally activated contact reaction strongly depends on the application of the capping layer. Contacts annealed without capping layer become ohmic at 420 °C. In the uncapped system, the contact reaction is dominated by the Au–GaAs interaction, as indicated by the appearance of Au7Ga2phase and large arsenic losses. Moreover, tellurium is shown to partly evaporate during the heat treatment. For the sealed contacts, the losses of both Te and As are limited. Suppression of As vaporization restrains the Au–GaAs reaction, while reduction of Te sublimation activates the Te–GaAs reaction. Ga2Te3and As2Te3are the main reaction products, apart from unreacted Au. These reactions, however, do not lead to the formation of ohmic contacts ton‐GaAs. Our results do not support the heterojunction model of ohmic contact, but rather testify in favor of the doping model.

ISSN:0734-211X    

DOI:10.1116/1.586803

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The lateral distribution of focused‐ion‐beam implanted Si and Be atoms has been studied by measuring the electrical resistivity in grating structures. The gratings which were oriented perpendicular to the direction of the current flow were implanted with silicon and beryllium at 280 and 260 keV, respectively. They were implanted into semi‐insulating materials cut on and off axis, and then rapid thermal annealed. The lateral straggle was found to be less than 100 nm for Si and equal to 190 nm for the Be implants. The standard deviation of the lateral distribution was found to increase with the dose. This is attributed to a concentration‐dependent diffusion which results in an anomalously high diffusion coefficient. Comparison of the experimental parameters of the implanted distribution with values found in standard tables or calculated by a Monte Carlotrimcode seems to indicate that all simulations overestimate the lateral straggle at the expense of the penetration depth.

ISSN:0734-211X    

DOI:10.1116/1.586804

出版商:American Vacuum Society    

年代:1993

数据来源: AIP