摘要:

Secondary ion mass spectrometry (SIMS) is an excellent technique to characterize III nitride materials and devices (dopants, impurities, and composition). Using empirical standards, the ion yield trends are derived for III nitride matrices to enable quantitative and high precision characterization of both major and impurity elements. The technique can be employed to investigate the control of purity and doping, determine growth rate and composition, as well as reveal the structure of finished optoelectronic and electronic devices. SIMS is thus a powerful tool for failure analysis, reverse engineering, and concurrent engineering.

ISSN:1071-1023    

DOI:10.1116/1.589777

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

For the first time a comparison is made between the surface characteristics of layers simultaneously grown on nominal and on vicinal(111)Bsubstrates under the1×1reconstruction regime which provides flat surfaces for both orientations. The influence of growth temperatures, 600 and 700 °C, on surface characteristics is thoroughly reviewed based on an atomic force microscopy study. This study yields additional insight into results already reported on growth mechanisms occurring along these two orientations for the19×19growth regime. For the nominal(111)Blayers, it will be shown that monoatomic steps at the surfaces define large atomically flat plateaus at both temperatures. At 600 °C, growth will be shown to proceed mainly through the development of two-dimensional nuclei, which are limited in size to a critical value and can coalesce by a proximity effect. These nuclei will be shown to be much smaller at 700 °C, thereby turning the step flow into the main mechanism occurring at that temperature. For the vicinal orientation, monoatomic-stepped and step-bunched surfaces grown at 600 and 700 °C, respectively, will be obtained under our1×1growth conditions, the same as in the19×19regime.

ISSN:1071-1023    

DOI:10.1116/1.589780

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Fabrication of a prototypeGa0.47In0.53As/Al0.48In0.52As/InPdouble heterojunction bipolar transistor employing an embeddedn+/n−-InP:Si subcollector/collector region in an otherwise semi-insulating InP:Fe substrate was studied. The basic layer structure was accomplished by two sequential growth cycles on the basis of device qualityAl0.48In0.52As/Ga0.47In0.53Asgrown by molecular beam epitaxy (MBE) and InP grown by metalorganic molecular beam epitaxy (MOMBE). For the first time the embedded collector was implemented by truly selective infill growth into a substrate groove with vertical sidewalls defined by reactive ion etching (RIF) using MOMBE. Excellent layer morphology in combination with lateral interfaces without growth irregularities at the lateral substrate/collector interface were achieved in the [0-1-1] direction, while some minor facet formation due to slightly enhanced growth rates appeared in the [0-11]direction. The device layer stack was completed by large areaAl0.48In0.52As/Ga0.47In0.53AsMBE regrowth due to its ability to highly Be dope the GaInAs base when grown at reduced growth temperatures. Functional devices were obtained. Some degradation in the output characteristics could be directly correlated with inhomogeneities in the MBE regrown structure.

ISSN:1071-1023    

DOI:10.1116/1.589781

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Two kinds ofn-GaAs layers doped with Si to a level of1017 cm−3are grown by molecular beam epitaxy on GaAs substrates: those grown on substrates cleaned using low temperature electron cyclotron resonance (ECR) hydrogen plasma and those grown on substrates cleaned by conventional thermal treatment. Comparisons between the electrical properties of both layers are made by capacitance–voltage(C–V)measurement; optical deep-level transient spectroscopy (ODLTS); Van der Pauw and Hall effect measurements; and secondary ion mass spectroscopy (SIMS). It is found from SIMS analysis that for thermally cleaned wafers, C, O, and Si accumulate in the vicinity of the interface between the epilayer and the substrate, whereas only oxygen accumulates at the same interface in ECR-cleaned wafers. TheC–Vand Hall measurements reveal that the carrier concentration,n,as well as the electron mobility, μ, decrease in the vicinity of the interface for thermally cleaned wafers. These results can be explained theoretically by using a physical model in which Si donors are compensated by unintentionally doped C acceptors. On the contrary, no degradation ofnor μ is observed for ECR-cleaned wafers. In addition, ODLTS measurement reveals the presence of deep hole traps due to the transition metals Fe and Cu, and a continuously distributed interface defect state for thermally cleaned wafers, whereas such defects are not observed for ECR-cleaned wafers.

ISSN:1071-1023    

DOI:10.1116/1.589782

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The nonselective wet chemical etching of AlGaInP and GaAs in pure iodic(HIO3)acid and in hydrochloric acid (HCl) associated different oxidant agents has been evaluated. The pure iodic acid is nonselective between III–V phosphides and arsenides. Unfortunately, the etch of GaAs results in a very rough morphology and an etch rate 10 times greater than on AlGaInP. The mixing of HCl with different oxidants such asH2O2gives a nonselective etchant. HoweverH2O2dissociates HC1 to form chlorine which produces a wide evolution of the etch rate with time incompatible with the reproducibility necessary for device technology. This phenomenon is easily explained and solved using oxidant agents such asKIO3, K2Cr2O7.Added to HCl, they give chemically stable solutions but unfortunately they give rise to a strong undercut of the AlGaInP under the GaAs. The iodic acid is also a strong oxidant. Therefore a diluted solution of(HCl, HIO3, H2O)is proposed which gives an evolution of the etch rate between 300 and 3000 Å/min with water dilution, a good stability in the time, and similar etch rates on the two materials with very good morphologies. Applied to heterostructure no undercut of the AlGaInP is observed.

ISSN:1071-1023    

DOI:10.1116/1.589783

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Pd/Zn/Au contacts top-In0.53Ga0.47As/InPwith various types of barrier layers to the indiffusion of Au have been examined by Rutherford backscattering spectrometry (RBS). For the metallizations with a barrier layer of Pd, the aging of the contacts at400 °Cfor 20 h produced a widespread indiffusion of Au for all thicknesses of the Pd. In comparison, the incorporation of a layer of Pt or amorphousLaB6in the contacts prevented an indiffusion of Au and significantly reduced any outdiffusion of the semiconductor elements. The presence of the barrier layer of Pt orLaB6produced little or no detrimental increase inρcfor this contact system. In the as-deposited Pd-based contacts, a layer of Zn in the structure was necessary in order to produce a minimum value ofρc.After annealing at500 °C,a specific contact resistance in the range8–10×10−6 Ω cm2was obtained for all of the contacts based on Pd/Zn/Au. A comparison has been made with the characteristics of Pt/Ti/Pt/Au contacts top-In0.53Ga0.47As/InPwhich were shown as stable against the indiffusion of Au.

ISSN:1071-1023    

DOI:10.1116/1.589784

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Using numerical treatment of experimentally obtained Fowler–Nordheim emission plots, radii of nanotips, formed by the build-up process in strong electric fields on the surface of the tungsten base cathode were determined. It was found that the typical size of such structures depended upon the conditions of their forming and was in the range of 10–50 Å. The field emission characteristics of these emitters for extremely high electric fields and current densitiesJwere studied. Studies of the emission current kinetics from a single nanotip show that atJ>Jblunting∼3–5×109 A/cm2an irreversible change of the tip submicrogeometry—“blunting” of the nanoemitter—takes place. Its apex radius increases 3–5 times. The maximum attainableJvalues from nanotips exceed the values for annealed substrate emitters up to 1 to 2 orders of magnitude. These values range from1010to1011 A/cm2depending on the size, structure, and geometry of tips. The results are presented of numerical simulation of cathode thermal regime, using the heat-transfer equation approach. It has been shown, that the explosive destruction of emitter and initiation of the vacuum breakdown is due not to heating of nanotips by high-density emission currents but to the energy accumulation in the base emitter bulk. The theoretical approach has been developed to the description of energy extraction accompanying the emission from ultrasmall structures (smaller than the free-path length for electron-phonon scattering). It was found that the maximum value of the total emission current was practically constant for emitting object from∼10up to∼50 Åin size.

ISSN:1071-1023    

DOI:10.1116/1.589785

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Silicon field emitter arrays have been fabricated by a novel method employing a two-step tip etch and spin-on-glass etch-back process using double layered thermal/tetraethylorthosilicate oxides as a gate dielectric. Partial etching was performed by low viscosity photoresist coating and O2plasma ashing in order to form the double layered gate dielectric. A small gate aperture with low gate leakage current was obtained by the novel process. The height and the radius of the fabricated emitter was about 1.1μm and less than 100 Å, respectively. The anode emission current from a 256 tip array was 23μA (i.e., 90 nA/tip) at a gate voltage of 60 V. The turn-on gate voltage was 40 V. The gate current was less than 0.1% of the total current (i.e., gate current and anode current).

ISSN:1071-1023    

DOI:10.1116/1.589786

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A novel technique for a gated silicon field emission cathode is proposed in order to decrease the spacing between the tip and the gate electrode of the device, which leads to low voltage operation. This technique is based on the filling characteristics of the sputteredTi0.1W0.9layer, which is used as the gate electrode in the shadowed area surrounding the tip with good step coverage. This process is completely compatible to conventional 1.2 μm complementary metal–oxide–semiconductor standard processes. The experimental results indicate that the diameter of the gate hole is greatly reduced to a subhalf-micron dimension(∼0.4 μm)even when starting with an initial mask size of 1.2 μm. TheI–Vcharacteristics of the cathodes show low turn-on voltages(∼25 V)in high vacuum(<3.0×10−7 Torr).The Fowler–Nordheim plots also show good linearity.

ISSN:1071-1023    

DOI:10.1116/1.589788

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

An electric discharge inducing method along curved discharge paths in a vacuum using a laser beam has been found. The discharge path in the present method is considered to be controlled by the passage of thermoelectrons along the electric field. Therefore, the path can trace not only a straight line but also curved lines. The thermoelectrons are emitted from a metal plasma, which is generated by a laser beam irradiation onto a metal surface (an electrode). Based on the present inducing principle, the discharge can be induced from an anode even to the back surface of the cathode through a hole in the cathode.

ISSN:1071-1023    

DOI:10.1116/1.589789

出版商:American Vacuum Society    

年代:1998

数据来源: AIP