摘要:

The optical absorption coefficient of crystalline silicon near the band edge is determined to values as low as 10−7cm−1by sensitive photocurrent measurements on high efficiency silicon solar cells. Structure due to three‐ and four‐phonon assisted absorption processes is observed. Discrepancies between absorption coefficient values around 10−2cm−1reported in the literature are resolved. The role of disorder theory in understanding the absorption edge of crystalline semiconductors such as silicon is discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113125

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Homoepitaxial diamond films grown by chemical vapor deposition from12C and13C containing gases have been studied by Fourier transform infrared spectroscopy. A sharp absorption band observed at 3123 cm−1is attributed to a CH vibrational absorption. It resembles the previously observed 3107 cm−1absorption band in natural diamond. Isotopic replacement of carbon, hydrogen, and nitrogen by13C,2H, and15N reveals, that a CH center without nitrogen participation is responsible for this new absorption. Furthermore, new hydrogen related electronic transitions have been observed around 7300 cm−1. These lines shift to higher energies in13C crystals, in accordance with the increase of the electronic band gap. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113126

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied the quasi‐two‐dimensional exciton in ZnSe/ZnxMg1−xSySe1−y(x=0.85,y=0.21) single quantum wells (SQWs) by photoluminescence and photoluminescence excitation spectroscopy. Self‐consistent calculations of the peak energies for a series of SQWs give the conduction band discontinuity &Dgr;Ec=0.40&Dgr;Egand the binding energy of then=1 heavy‐hole excitonEb(hh1)=22.1 meV for an 8 nm well width. We believe that the binding energy of then=1 heavy‐hole exciton is smaller than the LO phonon energy our samples resulting in a very large exciton‐phonon interaction strength observed through the broadening of the exciton resonance with temperature. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113127

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrical properties of AlxGa1−xAs (0≤x≤0.44) grown by organometallic vapor phase epitaxy using trimethylamine alane as the Al precursor were investigated. High‐quality AlGaAs Schottky barriers were fabricated and characterized by current–voltage, capacitance–voltage, and deep level transient spectroscopy measurements. The epilayers showed excellent electrical characteristics with low overall trap concentrations. In particular, the AlxGa1−xAs layers contained very low concentrations of EL2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113128

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

GaAs1−xPx/AlyGa1−yAs (x=0.07–0.15,y=0.3) strained‐layer quantum wells have been grown on GaAs‐(111)B substrates by low‐pressure metalorganic vapor phase epitaxy and characterized by photoluminescence (PL) spectroscopy. Evident energy blue shifts of the excitonic transition peaks (some of them as large as 33 meV) were achieved by increasing the excitation power during the PL measurement. The large optical nonlinearity mainly due to the strain‐induced piezoelectric field screened by the photoexcited carriers, is comparable to, or larger than, the reported values for a self‐electro‐optical effect device or other (111)‐oriented strained‐layer quantum well structures which are composed of InGaAs/GaAs or GaAs/GaAsP. This fact indicates that our (111)‐GaAsP/AlGaAs strained‐layer quantum well is a good candidate for making optoelectronic devices like optical switches and modulators. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113129

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The room‐temperature minority carrier lifetimes have been measured on 6H SiC epitaxial layers with residualn‐type doping ranging from below 1014cm−3to above 1017cm−3. Lifetimes as high as 0.45 &mgr;s have been achieved for thick low‐doped material. The samples were grown by chemical vapor deposition using silane and propane or silane and methane in a hydrogen ambient. The minority carrier lifetimes were measured by monitoring the decay of the near‐band gap room‐temperature luminescence of the samples after excitation of a short laser pulse. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113130

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A hot‐carrier‐temperature model is proposed in this letter to calculate the dark current of ap‐type GaAs/Ga1−xAlxAs quantum‐well infrared photodetector. Hot‐carrier effects are incorporated inside both the mobile‐carrier concentration (by a two‐carrier‐temperature energy distribution) and the drift velocity. Results of our calculations are in good agreement with experimental data at four different lattice temperatures and for the entire measured range of applied electric field. The increase of mobile‐carrier concentration at a hot‐carrier temperature is found to be the prevalent cause of the rise in dark current at higher applied electric fields. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113131

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Sheet resistance, Hall mobility, and effective carrier concentration as a function of annealing parameters for boron or phosphorus ion implanted films of polycrystalline Si, Si0.75Ge0.25, and Si0.50Ge0.50films are presented. The films were ion implanted with boron or phosphorus at dosages between 5×1014and 4×1015cm−2, and then thermally annealed between 550 and 650 °C from 0.25 to 120 min. Boron doped films showed decreasing minimum sheet resistance with increasing Ge fraction, while phosphorus doped films exhibited the reverse trend. Both boron and phosphorus doped films showed minima as a function of anneal time. This is attributed to the competing processes of damage annealing versus dopant segregation. Poly‐Si0.50Ge0.50films achieved minimum resistance faster than poly‐Si films, and the lowest sheet resistances were measured in boron doped, poly‐Si0.50Ge0.50films. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113132

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

1/fnoise for most electronic systems is stationary in that repeated measurements of the noise power will give the same result within statistical uncertainty. In contrast, we have observed highly nonstationary 1/fnoise in the output current of a series of InP based heterojunction bipolar transistors (HBTs). We have applied higher order statistics to the non‐Gaussian fluctuations of these devices to probe the source of the intrinsic 1/fnoise. We find signatures of superimposed Lorentzians making up an otherwise featureless 1/fnoise spectrum consistent with generation‐recombination‐type noise in the base‐emitter region of the device. The nonstationarity of these devices scales inversely with the device size as would be expected for an intrinsic mechanism. We suggest that these techniques may be utilized to a greater extent in the future as device sizes are reduced. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113133

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The threshold current density and the characteristic temperature of strain‐compensated InGaAs/InGaAsP/GaAs QW lasers are investigated theoretically. These results are also compared with those of uncompensated InGaAs/InGaAsP/GaAs QW lasers. From this calculation, it was confirmed that strain‐compensated lasers have lower threshold current density and better performance at high temperature compared to uncompensated lasers. This is attributed to enhanced carrier confinement and weaker temperature dependence ofNthfor strain‐compensated lasers. The well number dependence of the characteristic temperature is dominant for lasers with relatively short cavity length. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114283

出版商:AIP    

年代:1995

数据来源: AIP