J. Bregman

Quantitative Auger analysis by depth profiling of line shapes: Application to native oxide‐InSb interfaces

We report on a technique developed for improving quantitative analysis of Auger electron spectroscopy data by monitoring line shapes, peak energies, and ratios, in addition to peak heights, as a function of sputtering time. The technique proves to be useful for analysis of InSb‐native oxide interfaces due to the sensitivity of the AES lines of the different constituents to their chemical state. Thus important information can be obtained on the detailed structure and composition of these oxides and their interfaces, specifically, concerning quantitative determination of interface boundaries. The technique is discussed with typical results and possible extension to other interfaces.

Characterization of interface states at III‐V compound semiconductor‐metal interfaces

Surface photovoltage spectroscopy (SPS) has been used for direct measurements of the extrinsic surface states within the band gaps of p‐InP (110) and (100) and n‐GaAs(110) before and after Al and Au deposition. The observed metal‐induced surface states are found to pin the Fermi level at monolayer coverages at Ev+0.83 eV for Au/p‐InP(110), Ev+1.10 eV for Al/p‐InP(110), Ec−0.94 eV for Au/n‐GaAs(110), and Ec−0.80 eV for Al/n‐GaAs(110). The Au/Al/p‐InP(110) structure, studied for the first time using SPS provides evidence of strong Al clustering upon the InP surface. Chemically etched and UHV‐cleaved p‐InP surfaces and Au interfaces are also compared. The correlation between the observed energy state positions and electrically measured Schottky barrier heights is discussed.

Studies of SiOx anodic native oxide interfaces on InSb

We have investigated a method for passivation of InSb by vacuum deposition of SiOx on native oxide layers grown by wet anodization. We show that this multilayer dielectric approach results in improved passivation properties. Results of high resolution Auger spectroscopy reveal important information on the layer structure and composition of this passivation film. Specifically, we report the experimental observation of SiO2 formation at the SiOx anodic oxide interface. The interfacial reaction is limited to a thin layer, about 10 nm thick. The SiOx oxidation proceeds by reduction of the native oxide and formation of elemental In and Sb. The electrical features observed in the C–V curves (such as flat‐band voltage, hysteresis, low‐frequency‐like response in the inversion region, and other deviations from the ideal curves) are explained in view of the oxidation states of In and Sb, observed at the oxide layers and at their interfaces. These correlations were used for characterization of the desired interlayer...

Effects of oxygen partial pressure during deposition on the properties of ion-beam-sputtered indium-tin oxide thin films

Ion‐beam‐sputtered indium‐tin oxide (ITO) films were studied as a function of the oxygen pressure PO2, during deposition. Analysis of electrical transport measurements, Auger electron spectroscopy (AES), and x‐ray photoelectron spectroscopy (XPS) show a self‐consistent correlation of all the results. With increasing PO2 a monotonous decrease is observed in the carrier density, which is found to be directly proportional to the oxygen vacancy concentration. This is based on a direct evaluation of the concentration of In unoxidized species in the film using AES and XPS. The moderate decrease of the electron mobility as PO2 is increased is also attributed to the change in the film oxidation state. The systematic relations between all the parameters investigated in this study yield a better understanding of the deposition process and point in the direction of achieving the best ITO films.

Origin and effects of interface traps in anodic native oxides on InSb

We have investigated the wet anodization of InSb under a large variety of oxidation parameters. Results of Auger electron spectroscopy (AES) show that the oxidation produces a mixed oxide film of In2O3 and Sb2O3 containing some unoxidized Sb. 1‐MHz capacitance‐voltage characteristics show low‐frequency‐like response of the oxide‐semiconductor junction in the inversion region. We have found a strong correlation between this response and the elemental Sb content in the oxide, as revealed by AES. We present a model which explains the role of the elemental Sb in terms of interface traps and charge transfer into the inversion layer. Furthermore, we describe the anodization conditions under which the combined effect is reduced and explain their role. The implications of this observation are discussed.

Observation of the trend of interface formation in anodic native oxide on InSb by marker experiments

We have investigated the trend of anodization of InSb by predeposition of a very thin Cr layer, acting as a marker. Results of Auger electron spectroscopy show that the oxidation process is carried out by oxygen in diffusion through the oxide film. The details and implications of this observation are discussed.

Fabrication and properties of indium oxide/n‐GaAs junctions

Indium oxide/n‐GaAs junctions have been prepared by deposition of indium oxide layers onto n‐type GaAs by means of reactive evaporation of In in the presence of oxygen. The electrical and structural properties and the chemical composition of the resulting junctions have been investigated as a function of the oxygen pressure and substrate temperature during deposition. The analytical tools employed were Auger electron spectroscopy, x‐ray diffraction, capacitance‐voltage measurements, and current‐voltage measurements in the dark at room temperature and elevated temperatures. The results show that the substrate temperature during deposition dominated the interface composition, especially the degree of In oxidation. The oxygen pressure mainly affected the oxide stoichiometry and the In oxidation state in the bulk of the oxide. The resulting changes in the oxide and interface properties had direct implications on the barrier height and the ideality factor of the junctions. The best diodes yielded barrier heigh...

Correlation between electrical and compositional properties of SiO2‐InSb interfaces

We have studied interfaces of n‐InSb with SiO2 films, obtained by low‐temperature chemical vapor deposition, using capacitance‐voltage measurements and Auger electron spectroscopy (AES). Improvements of electrical properties of MOS capacitors based on this system were sought by various pre‐ and post‐treatments. The results show that a methanol pre‐treatment causes significant improvements in the flat‐band voltage (VFB) of metal‐oxide‐semiconductor capacitors based on this system. In addition, thermal post‐annealing in oxidizing atmospheres also improved VFB. AES reveals that at the SiO2‐InSb interface there is a native oxide interlayer, the width of which was found to be reduced by a factor of 2–3 due to the specified treatments. Therefore, we attribute the VFB improvement to the reduction in the density of charges and traps due to the narrowing of the interfacial native oxide, in agreement with other recent results.

Oxide and interface properties of plasma-grown and wet anodic oxides of InSb metal/oxide/semiconductor devices☆

Abstract We studied and compared InSb oxides, grown by plasma and anodic processes, using capacitance-voltage measurements and high resolution Auger electron spectroscopy (AES). We developed a method for analysing the AES line shapes, peak positions and ratios of the various elements as a function of depth in the oxides. The analyses provide detailed new information on the oxide layer structure and composition ( e.g. interface widths and boundaries) and on changes in the chemical bonding. On the basis of investigations of a large number of samples, we find that the two oxidation processes produce similar films comprising mixed oxides with a defined In 2 O 3 -to-Sb 2 O 3 ratio of 1:3. The In 2 O 3 In and Sb 2 O 3 Sb interfaces overlap but do not coincide, with the former usually being wider and closer to the substrate than the latter. This partial overlap indicates a distinct antimony-rich indium oxide interface which may dominate the electronic properties of the metal/ oxide/semiconductor structures. The AES characteristics are in turn related to the observed electronic properties.

Interface characterization of InSb MOS structures

Abstract The electrical properties of MOS devices are critically dependent on the oxide-semiconductor interface. The preparation of suitable insulating layers of oxide or other material is essential for the performance of such devices and it is particularly difficult in the case of III-V compound semiconductors. We report a method of preparing an insulating layer on InSb by a plasma oxidation process. The oxidation method will be described as well as results of the analysis of the oxide-semiconductor interface by electrical and compositional techniques. Capacitance-voltage characteristics reveal the existence of interface states which are distributed near the conduction and the valence bands with a higher density near the former. Depth profiling of the oxide by Ar+ sputtering and Auger electron spectroscopy (AES) shows that the oxide is composed of a mixture of indium oxide with the antimony oxide. At the interface a transition region can clearly be observed, whose composition seems to be mostly indium oxide rich in metallic antimony. This information can be derived from the Auger line shapes and positions. We find AES to be an extremely helpful tool for this kind of investigation, in spite of the obvious disadvantages of ion sputtering, especially in the case of indium and antimony. Correlations of the AES data with the electrical analysis results are suggested.