摘要:

Heteroepitaxial InP layers were grown by metalorganic chemical vapor deposition on novel GaAs buffer layers on Si substrates. The GaAs buffers were prepared by molecular beam epitaxy and show a reduced threading dislocation density achieved by inserting one nanometer thick Si interlayers. The structural and optoelectronic properties of the heteroepitaxial InP layers, which were investigated by transmission electron microscopy, x‐ray diffraction, and photoluminescence spectroscopy, show improvements attributed to the optimized GaAs buffer layers.

ISSN:0021-8979    

DOI:10.1063/1.350814

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Stresses in zinc oxide (ZnO) films prepared by radio frequency (rf) magnetron sputtering have been studied using a bending beam technique. The stresses exhibited at room temperature have been found to be strongly substrate dependent. The films deposited on gallium–arsenide (GaAs) substrates have exhibited much less compressive stress than those on silicon. This was contrary to what was expected. This may be attributed to: as revealed by x‐ray diffraction experiments, the films grown on GaAs are less crystalline so that peening effect could occur less intensively during deposition. The stress varies with different processing conditions, especially substrate temperature and total gas pressure.

ISSN:0021-8979    

DOI:10.1063/1.350815

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A series of unintentionally doped Ga1−xAlxAs epitaxial layers grown by molecular beam epitaxy, having various Al compositions (0.15, 0.18, and 0.29), have been Li diffused at 300 °C. Capacitance–voltage techniques show that the initialn‐type doping concentrations (of the order of 1016cm−3) increase after diffusion by typically a factor 5 to 10 demonstrating that isolated Li interstitials do exist and behave as donors. However, secondary‐ion mass spectroscopy measurements show that the material contains 1019–1020Li cm−3, which indicates that a large fraction of the Li impurities is not electrically active. Thus Li also produces defects as revealed by the fact that free electrons are frozen in the diffused layers below 77 K. Search for the existence of Li associatedDXcenters deep defects related to the donor impurities has been performed by deep level transient spectroscopy. Only theDXcenters present before diffusion, i.e., associated with residual donor impurities, are detected in the layer of 0.29 Al fraction. This implies that either Li donors do not induce the existence ofDXcenters or electron emission from LiDXcenters occurs below 77 K.

ISSN:0021-8979    

DOI:10.1063/1.350816

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Silicon germanium (Si1−xGex) alloys have been grown by the floating zone method withxvarying from 0.5 to 20 wt %. Resistivity and Hall effect measurements have been carried out in the temperature range 80–410 K. The Hall mobility has been found to decrease with Ge concentration varying between 0.5 and 4.5 wt % and thereafter an increase has been observed. The Hall mobility has also been found to decrease with an increase in temperature in these alloys following theAT−yrelation, whereAis a constant andTis the temperature in K.

ISSN:0021-8979    

DOI:10.1063/1.350817

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Experimental studies by means of a constant photocurrent method (CPM) have been carried out on the deep defect states in undoped hydrogenated amorphous silicon (a‐Si:H). Assuming Gaussian energy distributions, two types of defect states (ST1 and ST2) have been found from careful analysis of CPM spectra; one of these states (ST1) is a neutral Si dangling‐bond (SiD0) state, and the other (ST2) is a negatively charged dangling‐bond‐like defect state located in the lower gap. ST2 lies deeper in energy by 0.1 eV, and has a narrower full width at half‐maximum (FWHM) when compared with ST1. Possible candidates for ST2 have been discussed by referring to the previous models of defects ina‐Si:H. The FWHM of ST1 (the SiD0state) does not always depend on the overall structural disorder estimated from Raman spectra. The energy position of the SiD0state measured from the valence‐band edge is almost independent of the optical band gap. Long exposure to light increases the density of ST1 (the SiD0state) and decreases that of ST2, which suggests that defect conversion proceeds during the illumination.

ISSN:0021-8979    

DOI:10.1063/1.350818

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The dark current characteristics of gallium arsenide doped with silicon and compensated with diffused copper were found to have a pronounced region of current controlled negative differential conductivity (ndc) similar to the characteristics of a thyristor. The resistivity of the semi‐insulating semiconductor was measured to be 105&OHgr; cm for applied voltages up to 2.2 kV, which corresponds to an average electric field of 38 kV/cm. At higher voltages, a transition to a stable high current state was observed with a current rate of rise exceeding 1011A/s. There is evidence of the formation of at least one current filament during this transition. A theoretical model based on drift diffusion and boundary conditions that allows double carrier injection at the contacts has been used to show that the observed negative differential resistance is due to the filling of deep copper acceptors. The model also shows that the ndc curves may be tailored by adjusting the copper concentration. Doping of GaAs with various concentrations of copper was shown to change the dark current characteristics in a way predicted by the model.

ISSN:0021-8979    

DOI:10.1063/1.351365

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

CuInSe2/CdS heterojunction diodes prepared entirely by chemical spray pyrolysis are investigated using admittance spectroscopy to obtain information on electrically active trapping centers within the CuInSe2. Because of the relatively large parallel leakage conductance associated with these devices, a frequency‐swept admittance technique (stepped in temperature) is employed to differentiate between the loss signal due to trapping centers and the loss due to parallel conductance. The frequency‐swept admittance technique is described and compared to the more conventional temperature‐swept method. The devices used in this study exhibit one‐sun efficiencies of 2.0%–3.0% and a forward current dominated by generation‐recombination processes within the space charge region. Admittance spectra indicate a dominant hole trap is located approximately 270 meV above the valence band of the CuInSe2.

ISSN:0021-8979    

DOI:10.1063/1.350824

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Diodes with shallowp+njunctions were contacted with titanium silicide films which were formed by ion beam mixing with germanium. The leakage current of these diodes was observed to be dominated by a generation mechanism in the space charge layer. Deep level transient spectroscopy and secondary‐ion mass spectroscopy measurements revealed that ion beam mixing with heavy ions leads to recoil implantation of titanium atoms into the silicon substrate. The temperature and reverse bias behavior of the leakage current could be consistently explained by Shockley–Read–Hall generation mechanism [Phys. Rev.87, 385, 387 (1952)] and by Poole‐Frenkel barrier lowering [Phys. Rev.54, 647 (1938)] of the double donor level Ti+/++atEv+0.2 eV.4

ISSN:0021-8979    

DOI:10.1063/1.350796

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Relations are presented for calculating electron and light‐hole energy levels in quantum wells on the basis of knowledge of the electron and light‐hole effective masses, the lattice constant, and the width of the well. The electron and light‐hole band nonparabolicity of semiconductors forming the well is accounted for. The nonparabolicity of the heavy‐hole band is neglected. The calculated values ofEn− LHnandEn− HHntransition energies are in good agreement with recently published experimental data for various AlxGa1−xAs‐GaAs, Ga0.51In0.49P‐GaAs, and In0.53Ga0.47As‐InP quantum wells.

ISSN:0021-8979    

DOI:10.1063/1.350773

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Electron‐beam‐evaporated aluminum/silicon oxide/silicon tunnel diodes with an initial oxide thickness of 1.3 nm have been annealed for up to 1 h at temperatures from 213 to 369 °C. They have been investigated by infrared grazing internal reflection (GIR) spectroscopy and current‐voltage measurements. The measured IR spectra were analyzed by computer modeling. All spectral features could be explained self‐consistently within a Al/AlOy/SiOx/Si layer model. In the as‐deposited state less than 0.6 monolayers of Al—O bonds are formed at the Al/SiOxinterface. A thermally activated reduction of the ultrathin oxide film by Al was observed. The changes in the current‐voltage curves induced by slight annealing (1 min at 213 °C) are accompanied by changes in the insulator‐bonding structure, which GIR is sensitive enough to detect.

ISSN:0021-8979    

DOI:10.1063/1.350774

出版商:AIP    

年代:1992

数据来源: AIP