摘要:

A numerical technique is developed to analyze the electronic state in coupled semi‐infinite semiconductor superlattices. It is found that the superlattice miniband shrinks to discrete energy levels near the surface, and localized electronic surface states with energy falling within the ministop gap exist under certain conditions. Numerical calculations are also compared with results from an exact eigenvalue equation.

ISSN:0003-6951    

DOI:10.1063/1.103911

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Etching characteristics of Si1−xGexalloys in ammoniac wet cleaning (RCA cleaning) were examined. The etching rate of Si1−xGexbecame larger with increasing Ge ratio (X). Temperature dependence of the etching rate was studied and the etching rate was large at high temperatures. However, no obvious difference was observed in the temperature dependence of Si1−xGexetching rate at different Ge ratio (X). A surface morhology degradation after RCA cleaning was observed at high Ge ratio (X). A stoichiometry change of Si1−xGexsurface after RCA cleaning was observed by x‐ray photoelectron spectroscopy (XPS). The etching rate increase and the surface morphology degradation are thought to be due to the rapid etching of Ge atoms at the top surface layer.

ISSN:0003-6951    

DOI:10.1063/1.103912

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Diodes with transparent top contacts were fabricated by depositing indium oxide layers onton‐type GaAs by means of reactive evaporation of In in the presence of oxygen. The electrical characteristics as well as the structural properties and chemical composition of the resulting junctions were studied using Auger electron spectroscopy, x‐ray diffraction, optical absorption, capacitance‐voltage, and dark current‐voltage measurements. The best diodes were obtained under deposition conditions of substrate temperature 250 °C and oxygen pressure 5×10−4mbar; these diodes exhibited a Schottky barrier height of 0.85 V with an ideality factor of 1.04. The indium oxide films were found to be polycrystalline and to have an electrical resistivity of 3×10−4&OHgr; cm and an optical transmittance above 90% over the whole visible range. The effect of deviations from the optimal deposition parameters on the diode properties is discussed.

ISSN:0003-6951    

DOI:10.1063/1.103913

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The photoluminescence (PL) spectra from modulated quantum well structures were observed. The modulated quantum well structure comprised a 4 monolayer (ML) modulated layer and an 18 ML GaAs layer between AlAs barrier layers. The modulated layer was grown by incorporating As into a Ga and Al mixture on an AlAs surface. The main peak energy of the PL spectra at 77 K showed a growth temperature dependence; a remarkable red shfit of the main peak energy was observed for samples grown at low temperature. The red shift of the PL peak energy indicates an increase in the effective width of the GaAs well. A rearrangement model of Ga and Al atoms on the AlAs surface during growth with As incorporation into the Ga and Al mixture is proposed to explain the growth temperature dependence of the PL peak energy.

ISSN:0003-6951    

DOI:10.1063/1.103894

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Amorphous SiNx:H films were prepared by rf glow discharge of SiH4‐NH3mixtures at 300 °C, and the SiH, NH, and SiN vibrational absorptions were investigated as a function ofx. The stretching absorption profiles due to SiH and SiN bonds are reproduced by a superposition of two components at around 2000 and 2100 cm−1, and of three components at around 750, 840, and 960 cm−1, respectively. The dependence of these intensities onxwas examined by means of a generation probability analysis on the basis of the random bonding model including SiH and NH bonds which play an important role in the film growth mechanism.

ISSN:0003-6951    

DOI:10.1063/1.104160

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Direct electrical characterization of 1‐&mgr;m‐thick Si+preamorphized and epitaxially regrown silicon layers has revealed a low concentration of residual deep‐level defects within the regrown layer. A deep‐level trap atEc−0.40 eV has been found associated with the amorphous‐crystalline boundary dislocation loops. In addition, a near mid‐gap trap atEv+0.54 eV, observed inp‐type samples, is believed to be responsible for a spatially localized generation current of ∼2×10−6A/cm2associated with the dislocation loops.

ISSN:0003-6951    

DOI:10.1063/1.103895

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Device quality SiO2films with a thickness of 15 nm have been thermally nitrided in NH3by a rapid thermal processing technique. The properties of the interface between these films and a Si substrate have been investigated by a conductance technique. The results show that the nitridation increases the density and time constant of interface states and enhances the fluctuation of surface potential, but changes the hole capture cross section only slightly. Specifically, nitridation introduces a peak of interface states at 0.25 eV below midgap and the energy dependency of hole capture cross section is suppressed. Using a patchwork model, the surface potential fluctuation can be well simulated and a surface charge nonuniformity with a long‐wavelength distribution may exist. These are consistent with the fact that nitridation induces a high oxide charge density. Experimental data show that all these properties depend on nitridation time and temperature.

ISSN:0003-6951    

DOI:10.1063/1.104161

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Misfit dislocations in the SiGe system are usually not dissociated. We present the first observation of a Lomer–Cottrell lock array in a Si/Si1−xGex/Si heterostructure (0.4<x<0.6). We describe the character of the stacking faults and the partial dislocations which form the locks.

ISSN:0003-6951    

DOI:10.1063/1.103896

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electronic transport properties and structural morphology of fast‐pulse excimer‐laser‐ crystallized hydrogenated amorphous silicon (a‐Si:H) thin films have been measured. The room‐temperature dark dc conductivities and Hall mobilities increase by several orders of magnitude at well‐defined laser energy density thresholds which decrease as the impurity concentration in the films increases. The structural morphology of the films suggests an impurity‐induced reduction of thea‐Si:H melt temperature as the origin of this behavior.

ISSN:0003-6951    

DOI:10.1063/1.103897

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The persistent photoconductivity of Si‐doped AlGaAs has been investigated by temperature‐dependent resistance and Hall effect measurements. After illuminating the samples at low temperature, we observe for the first time distinct structures in the temperature‐dependent carrier concentration during the subsequent heating process. These structures are interpreted in terms of the existence of differentDXlevels below the conduction‐band edge.

ISSN:0003-6951    

DOI:10.1063/1.103898

出版商:AIP    

年代:1990

数据来源: AIP