摘要:

We demonstrate the first room‐temperature low‐threshold continuous‐wave (cw) operation of Al0.3Ga0.7As/GaAs single quantum well (SQW) heterostructure lasers grown by metalorganic chemical vapor deposition (MOCVD) on Si substrates using techniques of SiO2back coating and thermal cycle annealing. The all‐MOCVD‐grown SQW lasers on GaAs/Si with etch pit density of 1.5× 107cm−2have threshold current as low as 55 mA (1.41 kA/cm2) under cw at room temperature. The SiO2back coating is effective to obtain excellent current‐voltage characteristics. Thermal cycle annealing is also found to improve the crystallinity of GaAs/Si and to contribute to room‐temperature cw operation of the lasers on Si substrates.

ISSN:0003-6951    

DOI:10.1063/1.103519

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report operation of what we believe is the first continuous‐wave laser which relies exclusively on cooperative upconversion by coupled ion trios to achieve population inversion.

ISSN:0003-6951    

DOI:10.1063/1.103520

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Picosecond duration laser pulses are used to generate ultrashort acoustic pulses in a bilayer metal film. Time‐resolved transient piezoreflectance measurements permit the observation of acoustic reflections from a metal‐metal interface within the film, as well as reflections from the film‐substrate interface. We show that our measurements are well described by an abrupt interface model of acoustic mismatch.

ISSN:0003-6951    

DOI:10.1063/1.103521

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Electron cyclotron resonance plasma sources are gaining widespread use in plasma processing because they offer high ion flux with controllable energy and thereby high etching and deposition rates with minimal damage. However, it is unclear how ion energy distributions evolve from source to wafer as a function of plasma parameters such as pressure, microwave power, and magnetic field strength. Therefore, we used Doppler broadened and shifted laser‐induced fluorescent line profiles to measure Ar+metastable ion velocity distributions downstream from a divergent magnetic field electron cyclotron resonance source. Spatially resolved distributions, measured at positions above and across a wafer platen, differ markedly from shifted Maxwell–Boltzmann functions. Ions are accelerated along the magnetic field direction by a weak (∼0.5 V/cm), ambipolar electrostatic field. The ion energy component perpendicular to the electric field corresponds to a temperature of only 0.46±0.10 eV. On the edges of the platen, the magnetic and electrostatic fields diverge causing angled acceleration of ions.

ISSN:0003-6951    

DOI:10.1063/1.103482

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In‐plane anisotropy of Langmuir–Blodgett (LB) films is affected by the arrangement of substrates when many samples are batch produced in one single trough. We examined the dichroic behavior for two different cases of the batch production. In the case of substrates aligned side by side, the dichroic behavior is similar to that in the single‐substrate production and agrees with the flow orientation model. In the face‐to‐face case, however, the tendency is quite different from both the single‐substrate production and the side‐by‐side case, clearly deviating from the theoretical predictions. This discrepancy is suggested to be due to a dead water area which should be formed around the stagnation point.

ISSN:0003-6951    

DOI:10.1063/1.103483

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Diamond (100) substrates have been fluorinated under ultrahigh vacuum conditions with both atomic and molecular fluorine. X‐ray photoelectron spectra of the resulting samples indicate that atomic fluorine, F, reacts efficiently at 300 K producing a saturation coverage of about three quarters of a monolayer (one monolayer &bartil;1.6×1015cm−2) after 40 monolayers exposure. The carbon fluoride adlayer is thermally stable to 700 K but slowly desorbs at temperatures above this. In contrast, molecular fluorine, F2, reacts quite slowly; a saturation coverage of less than one fifth of a monolayer is achieved after several hundred monolayer exposure to F2at temperatures from 300 to 700 K. Diamond surfaces saturated with fluorine atoms showed no loss of fluorine after sequential exposure to beams of H2and O2at temperatures between 300 and 700 K.

ISSN:0003-6951    

DOI:10.1063/1.104097

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of positiveandnegative bias stress on hydrogenated amorphous silicon nitride/hydrogenated amorphous silicon (a‐SiNx:H/a‐Si:H) structures are investigated as a function of stress time, and stress temperature. It is shown that bias stress induces a parallel shift of the capacitance voltage (C‐V) characteristics. The direction of theC‐Vshift depends on the sign of the applied stress voltage, while the magnitude of theC‐Vshift depends on stress time and temperature in a manner which is identical to that observed ina‐Si:H thin‐film transistors. In addition, it is shown that positive bias stress increases the number of localized states in thea‐Si:H mobility gap, but negative bias stress does not. However, the observed increase cannot account for the correspondingC‐Vshift. These results lead us to conclude that theC‐Vshift is not induced by dangling bond defects ina‐Si:H but rather by carrier trapping in the insulator.

ISSN:0003-6951    

DOI:10.1063/1.103484

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new computer program enables the evolution of oxygen distributions in separation by implanted oxygen (SIMOX) substrates to be simulated during implantation and also after high‐temperature annealing. The positions of the Si/SiO2interfaces have been calculated for implantation energies of 150 and 200 keV. Theoretical results are in good agreement with experimental data over a wide range of fluences. It is found that the use of multiple implantation and annealing cycles, in comparison with a single implantation stage, shifts the buried oxide layer towards the surface.

ISSN:0003-6951    

DOI:10.1063/1.104227

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Direct measurements of the desorption rate of gallium from GaAs and (Al,Ga)As during growth by molecular beam epitaxy at high temperatures have been made by modulated beam mass spectrometry. The activation energy for desorption is dependent upon the nature of the site from which the gallium is lost. From free gallium atoms not incorporated into the lattice, behavior similar to that encountered under equilibrium conditions for gallium over gallium or gallium over GaAs is observed. For gallium lost from the GaAs lattice the apparent activation energy is higher and is influenced by the arsenic flux reaching the surface.

ISSN:0003-6951    

DOI:10.1063/1.103485

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We perform a deep level transient spectroscopy (DLTS) measurement of the band‐gap energy distribution of the trivalent silicon defects (Pbcenters) on as‐oxidized ⟨100⟩ silicon wafers. By comparison with the ⟨111⟩ silicon surface, we isolate the energy distribution of thePb1center. Its acceptor level is found at 0.42 ± 0.02 eV from the conduction band while the acceptor level for the ⟨100⟩Pb0center is found at 0.22 ± 0.01 eV, a value smaller than at the ⟨111⟩ surface (0.33 ± 0.01 eV). We obtain new results about the capture cross sections of the ⟨100⟩Pbcenters by energy‐resolved DLTS trap filling experiments. The electron capture cross section of ⟨100⟩Pb1is determined for the first time (5×10−16cm2), while the electron capture cross section for ⟨100⟩ Pb0(8×10−15cm2) is found to be in agreement with earlier results.

ISSN:0003-6951    

DOI:10.1063/1.103486

出版商:AIP    

年代:1990

数据来源: AIP