摘要:

The equilibrium hydrogen surface coverage on Si(100) during silicon epitaxy using SiH4has been measured in a rapid thermal chemical vapor deposition reactor. The hydrogen coverage could be ‘‘frozen out’’ completely on the surface by a rapid cool‐down and pump‐down of the reactor up to temperatures of &bartil;575 °C; at temperatures above 575 °C only partial ‘‘freeze‐out’’ is achieved. Surface hydrogen was titratedinsituusing the reactor as a thermal desorption spectrometer. Epitaxial silicon films were grown in the temperature range 450–700 °C and the film growth kinetics was correlated with the equilibrium hydrogen coverage. The growth mechanism changes from the low‐temperature regime, where the surface is hydrogen covered, to the high‐temperature regime, where the surface is essentially clean.

ISSN:0003-6951    

DOI:10.1063/1.102719

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We measure the absorption of thin InGaAs/InP quantum wells with a well width between 0 and 20 A˚. The discretization of the transition energies due to the quantization of the well width by monolayers is clearly observed for both the heavy and light hole excitons. The dependences of the heavy and light hole transition energies on the InGaAs growth time are investigated and show striking differences. This is discussed in relation to the atomic steps at the interfaces of the wells. The measured heavy and light hole transition energies agree well with calculation, which takes the split‐off holes into account.

ISSN:0003-6951    

DOI:10.1063/1.102720

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Si was etched using an O2molecular beam according to the chemical reaction 2Si+O2→2SiO↑. The minimum etching temperature was decreased by 25 °C when a Ge layer had been deposited on a clean Si surface before etching. At 800 °C, the Ge‐coated Si surface was etched while the clean Si surface was not. The O2partial pressure during etching was 2×10−5Torr; the etching rate was about 80 A˚/min at 800 °C. Auger electron spectroscopy showed that the number of Ge atoms slightly decreased during Si etching. Ge atoms on the surface are thought to weaken Si back bonds by forming a thin Ge‐Si alloy layer on the surface. Undercutting at the SiO2mask edge was suppressed by this Ge predeposition technique at 800 °C because the sidewall without Ge was not etched at this temperature.

ISSN:0003-6951    

DOI:10.1063/1.102721

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have observed that the absorption spectra in bulk Fe‐doped indium phosphide differ considerably from those recorded on undoped andn‐type samples. In the former case it was seen that the absorption edge presents a tail whose shape depends on the concentration of iron atoms incorporated into the matrix. Based on this phenomenon, we present a new nondestructive method which can be successfully employed to measure the iron concentration in semi‐insulating InP.

ISSN:0003-6951    

DOI:10.1063/1.102722

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Hydrogen was incorporated into B‐dopedp‐type crystalline silicon in three different ways: boiling the sample in water, exposing the sample to hydrogen plasma, growing silicon in a hydrogen atmosphere. Al‐contact Schottky barrier diodes were made on both the hydrogenated and unhydrogenated samples. It was found that the Schottky barrier height (SBH) is increased due to the hydrogenation. The current‐voltage measurement showed an increase of 0.06–0.10 eV in the effective SBH and the activation energy measurement revealed an increase of 0.07–0.09 eV in the SBH under a forward bias of 0.15 V. If the silicon grown in a hydrogen atmosphere was thermal annealed at 650 °C to drive out hydrogen before Schottky metallization, then the SBH approached that of the unhydrogenated sample. It is demonstrated that the SBH in Al/p‐Si can be increased with hydrogen incorporated in silicon.

ISSN:0003-6951    

DOI:10.1063/1.102723

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In0.53Ga0.47As photodiodes grown on GaAs substrates have been fabricated and analyzed. The dislocation density in the InGaAs layer is 2×107cm−2. A lowest dark current of 3.8×10−4A/cm2at 10 V bias is obtained, which is very stable during a bias‐temperature test ofVb=−10 V,T=175 °C, andt=100 h. The quantum efficiency is more than 85% at &lgr;=1.3 &mgr;m. This device is expected to be practically used. The dark current has been successfully explained by the thermionic emission and thermionic field emission from traps at midgap. The diffusion length of holes in the InGaAs layer is explained by the recombination at dislocations with the finite recombination velocity ofS∼104cm/s.

ISSN:0003-6951    

DOI:10.1063/1.102724

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have used a series of all‐optical measurements to determine shallow acceptor, shallow donor, and midgap donor (EL2) concentrations. The validity of these measurements was then tested by comparing the predicted electron density to the measured Hall density. Resonant pumping of the first excited state of the polariton sharpened the photoluminescence spectrum sufficiently to allow a reliable measurement of the shallow donor to acceptor ratio. The absolute shallow acceptor, donor, and EL2 concentrations were determined by a series of absorption and luminescence measurements. The Fermi level and hence the carrier concentration was then deduced using the three‐level model of semi‐insulating behavior.

ISSN:0003-6951    

DOI:10.1063/1.102725

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An amorphous silicon field‐effect phototransistor is fabricated using a processing technology compatible with conventional amorphous silicon‐silicon nitride thin‐film transistors. The phototransistor has an offset structure between the source and gate electrodes, where light is absorbed to produce a photocurrent. In an electron accumulation mode, the photocurrent is greater than the dark current by three orders of magnitude. In addition, the phototransistor is found to have output characteristics showing good saturation. Typical photoconductive gain of this saturation current is 17.

ISSN:0003-6951    

DOI:10.1063/1.102726

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Monte Carlo simulations of electronic high‐field transport in Si are performed. Contrary to previous treatments of impact ionization, we do not employ the ordinary Keldysh formula [Sov. Phys. JETP21, 1135 (1965)] with a soft threshold, but rather a new expression, which is an explicit function of the wave vector of the initiating electron, is used. The calculation results of drift velocity, ionization coefficient, and quantum yield show excellent agreement with the experimental data. Our results strongly substantiate the idea that the ionization threshold is basically hard even in Si in the sense that the electrons rapidly ionize when they approach the threshold energies and that the softness of the ionization threshold is introduced through the wave vector dependence of the threshold energies.

ISSN:0003-6951    

DOI:10.1063/1.102727

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Aqueous HF etching of silicon surfaces results in the removal of the surface oxide and leaves behind silicon surfaces terminated by atomic hydrogen. The effect of varying the solutionpH on the surface structure is studied by measuring the SiH stretch vibrations with infrared absorption spectroscopy. Basic solutions ( pH=9–10) produce ideally terminated Si(111) surfaces with silicon monohydride ( 3/4 SiH) oriented normal to the surface. The surface is found to be very homogeneous with low defect density (<0.5%) and narrow vibrational linewidth (0.95 cm−1).

ISSN:0003-6951    

DOI:10.1063/1.102728

出版商:AIP    

年代:1990

数据来源: AIP