摘要:

Controlled amounts of nitrogen atoms have been incorporated at Si–SiO2interfaces by a new, low‐temperature (300 °C), remote‐plasma process, and corresponding improvements in device reliability are reported. Interfacial nitrogen‐atom concentrations, up to 1×1015cm−2, were obtained by a predeposition, remote plasma‐assisted oxidation using mixtures of N2O and O2. Auger electron spectroscopy and secondary ion mass spectrometry studies to analyze N‐atom concentrations at Si–SiO2interfaces are discussed. Also, the results of electrical testing of submicron,n‐channel metal–oxide–silicon field‐effect transistors fabricated with this new process technology are reported. We found that the incorporation of N atoms at the Si–SiO2interface increased current drive capability at high gate voltages but did not affect the threshold voltage of devices or the peak channel transconductance,gm. Device reliability, as measured by resistance to peakgmdegradation after hot‐carrier stressing, was found to increase with increasing N‐atom concentrations at the Si–SiO2interface.

ISSN:0734-211X    

DOI:10.1116/1.587813

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

In view of the urgent necessity to establish a suitable passivation technology applicable to compound semiconductor quantum structure surfaces, the latest version of the silicon interlayer based passivation process was applied to passivation of Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As near‐surface quantum wells (QWs). The process utilizes an ultrathin molecular beam epitaxy silicon/ultrathin photo‐enhanced chemical vapor deposition (photo‐CVD) silicon nitride double layer as the interface control layer together with a main passivation dielectric of thick photo‐CVD SiO2layer. The effectiveness of passivation was studied by comparing the photoluminescence (PL) intensities of passivated samples with those of unpassivated QWs that showed exponential decrease with reduction of surface‐to‐well distance. A complete recovery of PL intensity was achieved by passivation with a maximum recovery factor larger than 103, consistent with reduced interface state densities in low 1010cm−2 eV−1range recently realized on In0.53Ga0.47As metal–insulator–semiconductor capacitors using the same technique.

ISSN:0734-211X    

DOI:10.1116/1.587814

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Al0.3Ga0.7As/GaAs quantum well samples, irradiated by (100 eV) hydrogen ions at low exposure, have shown improved luminescence for times greater than two years, when stored at room temperature in atmosphere.Insitutemperature programmed desorption (TPD) was used to investigate the desorption of AsH3from an oxidized AlGaAs surface treated by hydrogen ions. Surface modification determined by TPD and Auger electron spectroscopy measurements was correlated withexsituphotoluminescence measurements to further determine the reasons underlying the long‐term room temperature durability of this treatment, as well as the stability of the hydrogen ion passivation at elevated temperatures. Results indicate the importance of the native oxide of the substrate, present during the hydrogenation process, and which may serve as an over‐passivation layer. However, the thermal stability study also indicates that this over‐passivation layer is not thick enough to prevent the degradation of the underlying substrate at elevated temperatures.

ISSN:0734-211X    

DOI:10.1116/1.587815

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Ge/Si heterostructures were grown on Si (001) by Sn‐submonolayer‐mediated molecular beam epitaxy (MBE) and characterized by a variety of techniques, in order to study the behavior of Sn surfactant during Ge and Si growth and its influence on Ge/Si interface quality. It was found that Sn strongly segregates to the growing surface of both Ge and Si and that the presence of Sn surfactant can effectively suppress Ge segregation into a Si overlayer and enhance the surface mobility of adatoms. These results suggest that Sn‐mediated epitaxy can be used as a viable method to produce Ge/Si superlattices, with an interface quality superior to those grown either by conventional MBE or with other types of surfactants.

ISSN:0734-211X    

DOI:10.1116/1.587816

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The desorption of hydrogen from the Si(100) surface is investigated. The hydrogen coverage is generated by the adsorption of atomic hydrogen, by the thermal decomposition of disilane, or during silicon epitaxy using silane in a rapid thermal chemical vapor deposition reactor. Temperature programmed desorption studies are then used to help yield information about the hydrogen surface coverage and the desorption kinetics of hydrogen. The desorption order of hydrogen is first order, consistent with previously reported single crystal studies. However, the activation energy for desorption of hydrogen from surfaces generated during Si epitaxy with SiH4is considerably different. The activation energy for hydrogen desorption from these epitaxially grown layers is 49±3 kcal/mol. The presence of monatomic steps on the surface, which are created during the temperature quench, is believed to play a role in this difference of activation energies. Single crystal, ultra‐high vacuum based studies using atomic hydrogen and disilane adsorption and desorption are used to gain further insight into this phenomena.

ISSN:0734-211X    

DOI:10.1116/1.587817

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The evolution of surface roughness during growth of Ge(001) by molecular beam epitaxy at 155°C is characterized usinginsituscanning tunneling microscopy. The range of film thickness studied spans more than three orders of magnitude, 0.1–200 nm. Beginning at a film thickness near 100 nm, a periodic pattern of growth mounds is observed. The average in‐plane separation of growth featuresdevolves continuously with film thicknesst, following a power lawd=t0.42. The vertical roughness of the film does not follow a single power‐law behavior over this range of film thickness.

ISSN:0734-211X    

DOI:10.1116/1.587818

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Temperature‐programmed desorption (TPD) measurements are carried out in a molecular beam epitaxy (MBE) growth chamber on pseudomorphic GaAs/In0.22Ga0.78As(125 Å)/GaAs single quantum wells in various stages of growth, using a line‐of‐sight mass spectrometer for quantitative desorption analysis. The presence of surface‐segregated indium is inferred from the appearance of a relatively low binding energy (Eb≊1.5 eV) peak in the indium TPD spectra. Integration of this TPD peak provides a quantitative measure of the surface‐indium population ΘIn. By incorporating the TPD experiment as a subroutine in the MBE growth program, systematic variations of growth parameters are effected and their influence on ΘInestablished. Detailed composition profiles are calculated and found to be in excellent agreement with previous results [Nagleetal., J. Cryst. Growth127, 550 (1993)]. We find that both the bottom (InGaAs on GaAs) and top (GaAs on InGaAs) interfaces are graded over as much as 10 monolayers, with the bottom interface being indium‐poor, due to the sacrificial buildup of ΘIn, and the top interface being characterized by segregation of indium into the GaAs cap, due to relatively slow incorporation of ΘIninto the lattice after closing the indium shutter. A more ‘‘squarelike’’ bottom interface is obtained by predeposition of a thin indium layer just before InGaAs growth, while a more ‘‘squarelike’’ top interface is obtained by ‘‘flash‐off’’ of ΘInjust after InGaAs growth. It is believed that the combination of predeposition plus flash‐off produces a more truly square InGaAs/GaAs quantum well than that obtained by more standard MBE growth approaches.

ISSN:0734-211X    

DOI:10.1116/1.587819

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Cross‐sectional scanning tunneling microscopy has been used to investigate the effects of several key growth parameters on the resulting interfacial quality of AlAs/GaAs short period superlattices. For growth on top of AlGaAs layers, only superlattices grown with periodicity no smaller than 4 unit cells of GaAs and 2 unit cells of AlAs and grown with a minimum of 30 s of growth interrupt time are resolved. On the other hand, when grown on top of GaAs layers, superlattices as fine as 2 unit cells of GaAs and 1 unit cell of AlAs grown with only 5 s of growth interrupt time are resolved. This result suggests that the material on which the superlattice is grown is at least as important as the growth interrupt time. In particular, GaAs seems to provide a smoother starting surface than AlGaAs and hence aids in the formation of abrupt interfaces. We also compare our scanning tunneling microscopy data with some predictions based on simple atomic models of the interfacial regions.

ISSN:0734-211X    

DOI:10.1116/1.587820

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The tip of a scanning tunneling microscope (STM) was used to inject electrons into thin Pt layers of metal–oxide–semiconductor (MOS) structures. The collector currents emanating from then‐type Si(100) substrates were measured as a function of the electron energy, determined by the STM tip biasVT, for different oxide biasesVoxapplied independently across the oxide layers. The SiO2layers were thermally grown in a device processing line and ranged from 27 to 62 Å in thickness. A current threshold nearVT=3.90 V is interpreted in terms of current transport through the SiO2conduction band. The current transport through the MOS structure was modeled in a single band description for zero oxide thickness, and fitted to the collector currents that had been corrected for impact ionization effects in the Si. Deviations between the two curves represent the influence of the transmission probabilityToxthrough the SiO2film of finite thickness.Toxcan thus be determined from the experimental data. Within an eV of threshold the magnitude ofToxwas observed to be particularly sensitive to small changes in oxide bias in the range 0.3 V≳Vox≳−0.1 V. The transmission probabilities were also calculated by integrating the Boltzmann equation using Monte Carlo techniques that incorporate energy dependent effective masses and electron phonon scattering rates. Agreement between the two approaches is quite good, including the observed sensitivity on oxide bias in the threshold region, which is a direct consequence of the strong electron‐optical phonon scattering in the oxide. The 27 Å thick oxide structures exhibited in the ballistic electron emission microscopy images scattered patches of high transmittance of only 1–2 nm in extent. The collector currents arising from injection at these patches indicated thresholds as low as 1.1 eV, but the observed modest currents above that threshold argue against local shorts that would arise from pinholes in the oxide.

ISSN:0734-211X    

DOI:10.1116/1.587821

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We investigate the dependence of the average interface field on the inversion and depletion charge density through the use of a zero‐temperature Green’s function formalism for the evaluation of the broadening of the electronic states and conductivity. Various models for the surface‐roughness autocovariance function existing in the literature, including both Gaussian and exponential models, are studied in our calculations. Besides surface‐roughness scattering, the dominant scattering mechanism at high electron densities, charged impurity, interface‐trap and oxide charge scattering are also included. The position of the subband minima, as well as the electron wave functions, are obtained by a self‐consistent solution of the Schrödinger, Poisson, and Dyson equations for each value of the inversion charge density. Many‐body effects are included by considering the screened matrix elements for the scattering mechanisms and through inclusion of the exchange‐correlation term. The dependence of the mobility and the effective field upon the inversion charge density is sensitive to the model chosen, and we discuss the manner in which this may be used to study the interface itself.

ISSN:0734-211X    

DOI:10.1116/1.587822

出版商:American Vacuum Society    

年代:1995

数据来源: AIP