摘要:

Excited neutral nitrogen species emitted from a rf plasma source were characterized by the laser-induced fluorescence (LIF) spectroscopy, while nitrogen ions were detected by the ion counting method. The LIF intensity for nitrogen molecules increases monotonously up to the rf power of 100 W and saturates over 100 W. On the contrary, ion count of nitrogen ions shows a gradual increase up to 100 W, then rapidly increases above 100 W. The correlation between the number of excited nitrogen species and the net acceptor concentration(NA−ND)of nitrogen doped ZnSe epitaxial layers for various rf powers has been studied. We confirm that the excited neutral nitrogen molecules are effective for acceptor doping, while nitrogen ions enhance carrier compensation presumably due to degradation of crystal quality. We show that the activation ratio{(NA−ND)/[N]}ofp-ZnSe:N is greatly improved by removing ions from the nitrogen plasma. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119586

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Laser emission was observed in photonic semiconductor dots with a discretized optical mode spectrum. The photonic dots with lateral sizes between 1 and 5 &mgr;m provide a three-dimensional optical confinement by using in the vertical direction AlAs/GaAs Bragg mirrors and in the lateral directions the refractive index discontinuity at the etched surfaces. In the optically pumped structures, the laser emission takes place on the fundamental mode of the microcavities. External threshold excitation densities of200 W/cm2,which correspond to a very low internal optical excitation power of 0.15 &mgr;W per microcavity post, were measured for microcavity structures with a lateral size of 2.7 &mgr;m. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119587

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A direct measurement of carrier recombination, far from equilibrium, inHg0.795Cd0.205Te(Nd−Na=3.3×1014 cm−3)has been made on a picosecond time scale with a pump–probe technique using a free-electron laser. Over the range of carrier densities(5×1016–3×1017 cm−3)and at the temperatures (50–300 K) studied experimentally, contributions to the recombination from Auger, Shockley–Read–Hall, and radiative mechanisms were calculated using an analytic approximation, with carrier degeneracy included, Auger-1 (CCCH) recombination rates were calculated, which also gave the Auger-7 (CHHL) rates via a simple relationship. Excellent agreement was obtained, with Auger-1 dominant at all temperatures and, significantly, forT>225 Kwhen the sample is intrinsic, the Auger-7 contribution was found to be important. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119588

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have successfully used a thin layer (∼200 Å) of annealed low-temperature GaAs (LT-GaAs) to reduce ion damage that would occur during the formation of a dry-etch gate recess of a high electron mobility transistor. Compared to structures without an ion damage blocking layer, the devices with a thin layer of LT-GaAs are more robust against ion damage. This is important for the application of ion-assisted processing to the fabrication of electronic devices, such as dry etching used to achieve gate recessing. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119608

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A method of producing lateral confinement of an electron gas has been realized by using molecular beam epitaxy to grow a high mobility heterostructure on a (100)n+-GaAs layer selectively etched to create a two-dimensional array of cavities through then+-GaAs, which are bound by higher index facets. Far-infrared cyclotron resonance (CR) spectra unambiguously demonstrate that the electron gas formed inside the cavities is confined in both lateral directions. Typical confinement energies of30 cm−1and widths of 2000 nm are derived from the spectra and magnetoresistance measurements. The effect of differentn+-GaAs backgate biases is also investigated. Combining information from CR spectra with atomic force microscopy images provides a picture of the nature of the lateral confinement in this structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119589

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Defect states responsible for leakage current in ultrathin (physical thickness <10 nm) tantalum pentoxide(Ta2O5)films were measured with a novel zero-bias thermally stimulated current technique. It was found that defect statesA,whose activation energy was estimated to be about 0.2 eV, can be more efficiently suppressed by usingN2Orapid thermal annealing (RTA) instead of usingO2RTA for postdeposition annealing. The leakage current was also smaller for samples withN2ORTA than those withO2RTA for postdeposition annealing. Hence, defect statesAare quite likely to be important in causing leakage current. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119590

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The reduced effective masses inInxGa1−xAs/InPquantum wells have been determined as a function of strain (xvalue) and well width by means of magneto-optical methods. Magnetoexcitons have been observed in photoluminescence excitation spectra in the presence of a magnetic field. At higher magnetic fields, the observed magnetoexcitons will asymptotically approach the free Landau levels. From a least square fit, the dependence of the reduced effective masses on strain and well width has been deduced. Also, the reduced effective mass including the light hole state has been determined for the tensile strained quantum well structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119591

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Improved isothermal capacitance transient spectroscopy (ICTS), which measures the entire capacitance transient as a function of time and temperature in a single temperature scan, has been implemented in a deep level trap analysis extending the characterization to include capture barrier measurement. This method eliminates inaccuracies introduced by narrow pulse widths that are difficult to reproduce accurately, providing capture barrier information more accurately and easily in addition to the usual deep level characteristics. A method of establishing ICTS experimental conditions and a method of analyzing the resulting data are described and applied to the investigation of deep levels in Te-dopedAlAs0.07Sb0.93.The sample shows a single DX center trap having a deep level energy of 278 meV, a high temperature capture cross section of1.3×10−12 cm2,and a capture barrier energy of 137 meV, clearly demonstrating the superior method of measuring a capture barrier. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119592

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple wet chemical etch which produces stable and oxide-free surfaces of ZnSe is described. The etchant, a lowpHsolution ofH2SO4:H2O2:H2O,reacts with ZnSe producing an amorphous layer of Se which grows into the semiconductor. The Se layer is then dissolved in aqueous(NH4)2Sresulting in a S-passivated surface. The S-passivated layer is volatile and can be desorbed by heating the sample to 300 °C. The efficacy of this process is demonstrated by the formation of 20 nm wide quantum wires of CdZnSe/ZnSe with good optical properties. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119593

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have investigated the resonant interband tunneling current in InAs/AlSb/GaSb/AlSb/InAs double-barrier resonant interband tunneling diodes with extremely thin AlSb barriers. Although no negative differential resistance (NDR) was observed for the diode without AlSb barrier layers, NDR appeared when 0.5-monolayer(ML)-thick AlSb barrier layers were inserted. As the thickness of AlSb barriers(Lb)increased from 0.5 to 2 ML, the difference between the peak current density and the valley current density increased. This result indicates the crucial role of the extremely thin AlSb barrier layers that are responsible for the resonance level and move it up toward the GaSb valence-band edge with an increase inLb.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119594

出版商:AIP    

年代:1997

数据来源: AIP