摘要:

InxGa1−xP layers lattice matched and lattice mismatched to GaAs substrates have been grown by metalorganic chemical vapor deposition (MOCVD). Deep level transient spectroscopy, double crystal x‐ray diffraction, and current–voltage measurement were employed to characterize InxGa1−xP layers and InxGa1−xP/GaAs heterojunctions. We have observed a shallow electron trap located atEC−60 meV in InxGa1−xP layers withx<0.469, and a deep electron trap atEC−0.85 eV withx≳0.532. However, no deep levels were detected in InxGa1−xP (0.469

ISSN:0734-211X    

DOI:10.1116/1.588131

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

InP(100) surfaces were S passivated in S2Cl2, (NH4)2S and sulfide‐containing Br2solutions. After S2Cl2treatments, observations using atomic force microscopy indicated that the sample surface was rougher than the as‐received sample. Some residual oxide was also identified by Auger electron spectroscopy and x‐ray photoelectron spectroscopy analysis. Treatment of InP(100) in (NH4)2S and Br2/MeOH solutions containing trace amounts of S2Cl2and (NH4)2S significantly reduced the surface roughness of the as‐received sample. These treated surfaces were also found to be free of oxide and S passivated. These solutions therefore effectively removed the native oxide leaving substrates approaching atomic flatness and subsequently passivated surfaces with sulfur from the solution.

ISSN:0734-211X    

DOI:10.1116/1.588132

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We have examined by transmission electron microscopy In0.48Al0.52As layers grown by molecular beam epitaxy on (100) InP substrates. The characterization of the nature of the crystal defects (dislocations and stacking faults) observed in the layers, and the study of their asymmetric distribution in the 〈011〉 directions point towards the differentiation of two mechanisms for defect nucleation and therefore towards two models explaining the observed anisotropy depending on the growth temperature (Tg). Then, for lowTg(300 °C) we have observed a {11̄1}‐microtwinned structure whose origin has been explained taking into account the limited kinetics of III atoms during the growth and the differences in the propagation speed of the surface steps during the molecular beam epitaxy growth. For growth temperatures in the 440–530 °C range, the defect densities decrease monotonically, being threading dislocations and stacking faults on the (11̄1) and (111̄) planes the prevalent type of defects. The asymmetry of fault densities between the {11̄1} and {111} planes have been discussed on the basis of the different mobilities of the partial dislocations bordering the faults.

ISSN:0734-211X    

DOI:10.1116/1.588133

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

In this work, we present the Hall electrical properties for molecular beam epitaxy grown modulation‐doped field‐effect transistors structures using a short‐period superlattices channel of (InAs)1.1±0.1(GaAs)nwhere the indexes 1.1 andnrepresent the number of InAs and GaAs monolayers, respectively. These properties are compared with those of structures using the alloy in the channel and the variables were the indium content (y=0.08±0.01–0.25±0.01) and the channel thickness (80–150 Å). The mobility and the free carrier concentration were obtained as a function of the illumination intensity of a light‐emitting diode at 77 K. Our results indicate that for indium content aroundy=0.08±0.01, the electrical properties are independent of using short‐period superlattices or alloy channels. For an indium content aroundy=0.25±0.01 the electrical properties change significantly for the two structures. For the same carrier concentration (n=2.8×1012cm−2), we observed for the sample having the short‐period superlattices structure mobilities 33% higher than those for the alloy structure. Our conclusion is that the scattering associated with the alloy disorder increases with the indium content and that this deleterious effect can be reduced, replacing the alloy layer with short‐period superlattices.

ISSN:0734-211X    

DOI:10.1116/1.588134

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Atomic layer passivation (ALP) with atomically thin P‐related compound semiconductor materials grown on (100) GaAs surfaces significantly enhances the photoluminescence intensity and also makes the electrical characteristics of GaAs metal–insulator–semiconductor (MIS) diodes (M/I/ALP/GaAs) nearly ideal. This study clarifies the change in GaAs interface characteristics caused by introducing As and subsequent passivation. Arsenic is introduced to GaAs surfaces by heating wafers in an AsH3atmosphere before forming the passivation layer. Due to the As introduction, the enhancement of the PL intensity is suppressed to the magnitude of the intensity from conventional GaAs surfaces. The influence of As introduction on surface Fermi level pinning was also studied by fabricating MIS diodes. It is found that the range of capacitance becomes narrower than that observed in MIS diodes with ALP without an As layer. High‐frequency analyses show that the surface Fermi level can move only within a limited energy range of 0.6 eV from the conduction band minimum of GaAs. It is shown that a reduction in the amount of As at the interface is necessary to unpin it in the ALP/GaAs system. The characteristics of As‐induced interface states are discussed.

ISSN:0734-211X    

DOI:10.1116/1.588135

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

n‐ andp‐doped GaN thin films have been epitaxially grown onc‐sapphire substrates by metal‐organic chemical‐vapor deposition in a production scale multiwafer‐rotating‐disk reactor. Theinsitudoping was performed with material having a low background carrier concentration ofn∼mid‐1016cm−3. Biscyclopentadienyl magnesium (Cp2Mg) and disilane (Si2H6) were used as the precursors for thepandndopants, Mg and Si, respectively. The effect of mole flow on material, electrical, and optical properties was studied. We observed that bothn‐ andp‐type doped GaN exhibited an excellent surface morphology, even with a high mole flow of doping precursors. After the Mg‐doped GaN was annealed in a N2ambient at ∼700 °C for 30–60 min, the highly resistive GaN was converted intop‐type GaN with a low resistance of 0.1–1.0 Ω cm. Transmission electron microscopy showed that the defect density on the annealed Mg‐doped GaN is only 4×109cm−2which is of the same order as undoped GaN (1.5×109cm−2). One of the bestp‐GaN samples has a Hall carrier concentration of 5.2×1018cm−3and a hole mobility of 20 cm2/V s, which are the best values reported in the literature to date. The photoluminescence spectra ofp‐GaN show a strong band edge at 430 nm with a full width at half‐maximum of 300 meV at room temperature.

ISSN:0734-211X    

DOI:10.1116/1.588080

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Al–Ni–Ge ohmic contacts onn‐GaAs were prepared by sequential vapor deposition and furnace annealing at 500 °C. The metallurgical properties of the contacts were studied by transmission electron microscopy. It was found that while Al–Ni–Ge as a whole is relatively stable against GaAs, extensive interfacial reactions readily occur within the contact layers, resulting in a very stable layered structure of the type Al3Ni/Ni–Ge/GaAs, with ε′‐Ni5Ge3being the major phase in the Ni–Ge layer. GaAs twins and Ni–As precipitates were found in a thin layer immediately below the metallization, suggesting that the ohmic behavior can be accounted for in terms of a GaAs regrowth mechanism.

ISSN:0734-211X    

DOI:10.1116/1.588081

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The thermal stability of nonalloyed Mo/Au and Ti/Pt/Au contacts onn+InGaAs, ranging in thickness from 3 to 50 nm, was investigated for a heterojunction bipolar process. Layers of highly silicon doped InGaAs were grown onn+GaAs by molecular beam epitaxy, without a compositionally graded layer between the InGaAs and GaAs. The as‐deposited contact resistance exhibits a strong dependence on InGaAs thickness. For In0.5Ga0.5As, as the InGaAs thickness increases from 6 to 20 nm, the contact resistance decreases from 8×10−7Ω cm2to as low as 2×10−7Ω cm2. Ohmic contacts with various InGaAs thicknesses, InGaAs composition, and contact metallurgies were heat treated at 300 °C for times of 2 h or more. The contact resistivity of MoAu on In0.5Ga0.5As contact layers that are thinner than 20 nm shows poor thermal stability, increasing as much as 160% for a 6 nm thick layer of InGaAs. Contacts on a pseudomorphic InxGa1−xAs layer of the same thickness, but with a lower In mole fraction ofx=0.35, exhibit better thermal stability, increasing by only 15% in contact resistivity with heat treatment. Stable contacts can also be obtained by making the In0.5Ga0.5As thickness at least 20 nm. Cross‐sectional transmission electron microscopy (TEM) of 20 nm InGaAs films heat treated at 300 °C for 2 h reveals a virtually unchanged Mo–InGaAs interface. TEM analysis of TiPtAu contacts shows that the Ti/InGaAs interface and the InGaAs layer thickness become increasingly nonuniform with thicker titanium layers. This physical degradation correlates to an increase in the contact resistivity. The increase in contact resistivity can be minimized by reducing the Ti thickness to 5 nm or less. For extended anneals at 300 °C for accumulated times of 397 h, MoAu on 20 nm of In0.5Ga0.5As demonstrates better stability in contact resistance than Ti (5 nm)/Pt/Au on 20 nm of In0.5Ga0.5As.

ISSN:0734-211X    

DOI:10.1116/1.588082

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A phenomenological model of grain‐boundary diffusion and electromigration in thin‐film diffusion barriers for microelectronic device metallizations is developed by using the transmission line matrix method. Both diffusion and drift effects are included in the numerical analysis with a multidimensional variable mesh structure. Special attention is paid to the ‘‘vertical’’ electromigration effect and a comparison of the two‐dimensional (2D) and three‐dimensional (3D) simulation results. Two fundamental driving forces for impurity grain‐boundary diffusion, the concentration gradient across a diffusion barrier, and the current flow perpendicular to the deposited metal films can reinforce each other, leading to an enhanced impurity diffusion and a reduced barrier efficiency. Such material transport through the diffusion barrier is quantified with a 2D model of parallel planar grain boundaries and a 3D model of rectangular columnar microstructures. Concentration profiles along all directions are visualized in graphs for the cases with and without the electromigration driving force. Average atom penetration as a function of time and the underestimation by the 2D model are also illustrated.

ISSN:0734-211X    

DOI:10.1116/1.588083

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Chemical vapor deposition (CVD) TiN is an attractive replacement for PVD TiN as a barrier and glue layer for subhalf‐micron contacts and vias. CVD TiN films have been deposited in a commercial reactor via the thermal decomposition of tetrakis‐dimethyl‐amino‐titanium (TDMAT) precursor in an N2ambient. The deposition can be characterized by a simple Arrhenius rate expression with a half‐order dependence on TDMAT concentration and an activation energy of 0.53 eV. Designed experiments show that the deposition transitions from being kinetically limited at high TDMAT flow rates and low temperatures to transport limited at the other extreme. In the kinetically limited regime, the deposition rate increases with increasing TDMAT mole fraction and increasing temperature. Step coverage simulations have been performed by couplingSPEEDIE(a profile evolution program) with the Arrhenius rate expression. Experimental and simulated step coverages show good agreement over a wide range of process conditions. Step coverage improves with increasing deposition rate and decreasing temperature. Adequate deposition rates (≳400 Å/min) with good deposition uniformity and high step coverage (50%–85%) can be achieved. Film stress and roughness are mostly invariant with process conditions. These films are close to stoichiometric (i.e., 1:1 Ti:N ratio), but contain up to 30% carbon. Exposure of these films to air causes rapid oxidation with a steady state concentration of 15%–20% oxygen after 24 h of air exposure.The high carbon concentration results in high film resistivity (5000 μΩ cm), which doubles after 24 h of air exposure due to oxidation of the film. Film resistivity decreases and film stability improves with increasing N2flow rate. Electrical characterization of two process variants have been performed. The first provides a film with 85% step coverage with a resistivity of 5600 μΩ cm, while the second process achieves a lower resistivity of 3700 μΩ cm and a lower step coverage of 50%. Electrical performance of both films is similar. Contact induced diode leakage is lower for CVD TiN compared to PVD TiN. Contact resistance for 100–200 Å CVD TiN is comparable or lower than 500 Å PVD TiN. A 100 Å CVD TiN barrier is adequate; 300 Å CVD TiN is too thick because of high film resistivity. An Al–Cu/100–300 Å CVD TiN/Si stack shows lower resistance increase after 450–500 °C, 30 min N2anneal compared to a Al–Cu/200 Å PVD TiN/Si stack indicating that CVD TiN is a superior barrier and is more inert than PVD TiN.

ISSN:0734-211X    

DOI:10.1116/1.588084

出版商:American Vacuum Society    

年代:1995

数据来源: AIP