摘要:

Ultrafast hole relaxation dynamics is selectively investigated in intrinsic bulk GaAs using a high sensitivity two‐wavelength pump‐probe technique. Nonequilibrium carriers are photoexcited close to the bottom of their respective bands and hole heating is followed by monitoring the transient bleaching of optical transitions involving higher momentum states. Hole heating is found to be dominated by hole‐phonon interactions with a thermalization time of the order of 150 fs for carriers densities in the 1017cm−3range. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113201

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Semi‐insulating 6H–SiC crystals have been achieved by using controlled doping with deep‐level vanadium impurities. High resistivity undoped and semi‐insulating vanadium‐doped single‐crystals with diameters up to 50 mm were grown by physical vapor transport using an induction‐heated, cold‐wall system in which high purity graphite materials constituted the hot zone of the furnace. Undoped crystals werep‐type due to the presence of residual acceptor impurities, mainly boron, and exhibited resistivities ranging up to 3000 &OHgr; cm. The semi‐insulating behavior of the vanadium‐doped crystals is attributed to compensation of residual acceptors by the deep‐level vanadium V4+(3d1) donor located near the middle of the band gap. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113202

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on reverse biased photoconductive detectors with novel design and improved high‐frequency performance. Taking advantage of the ‘‘giant ambipolar diffusion constant’’ which has been observed previously inn‐i‐p‐idoping superlattices very fast carrier transfer from the inner absorption area to the outer detection area is achieved. The combination of narrow contact spacings and smallRCand diffusion time constants results in very high gain‐bandwidth products (≳20 GHz) with adjustable 3 dB frequencies. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113203

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of substitutional C on interstitial‐enhanced B diffusion in Si has been investigated. Substitutional C was incorporated into B doped Si superlattices using molecular‐beam‐epitaxial growth under a background of acetylene gas. Excess Si self‐interstitials were generated by near‐surface 5×1013/cm2, 40 keV Si implants and diffused at 790 °C. The interstitial‐enhanced diffusion of the B marker layers is fully suppressed for C concentrations of 2×1019/cm3, thus demonstrating that substitutional C acts as a trap for interstitials in crystalline Si. Uniform C incorporation of 5×1018/cm2significantly reduces the transient enhanced diffusion of a typical B junction implant without perturbing its electrical activity. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113204

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

High quality, homoepitaxial layers of 4H‐SiC have been grown by chemical vapor deposition in a hot‐wall reactor. The residual doping concentration obtained by capacitance versus voltage measurements was as low as 2×1014cm−3. The high quality is confirmed by photoluminescence measurements performed at low temperatures (1.8–4.2 K) showing strong free exciton related luminescence and by the fact that optically detected cyclotron resonance signals could be observed (at 6 K), as a result of the highest mobility reported in SiC. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113205

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Measurements of light emission are reported in the 1.1–2.5 eV energy range, by hot electrons in the In0.53Ga0.47As channel of a complementary charge injection transistor. By comparing electrical characteristics and light emission, there is the ability to identify the intraconduction band transitions as the main light emission mechanism. Hot‐electron effective temperatures up to 2200 K have been determined from high energy exponential tails of the electroluminescence spectra. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113206

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Results of transport measurements on a GaAs quantum dot are presented in which the gate geometry allows the dot to be accessed by three, rather than two, contacts. In the Coulomb blockade regime, conductance oscillations periodic in gate voltage are measured concurrently at two contacts in response to a small excitation voltage at the third contact. When the dot is in the strongly blockaded regime, we obtain the expected result from single electron tunneling theory that oscillations at the two output contacts are correlated with each other in gate voltage. As the tunnel barriers are made softer by changing the gate voltage, a strikingly different phenomenon is observed: conductance peaks at the two output leads evolve from perfect correlation to perfect anticorrelation with each other. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113207

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Uniform arrays of approximately 57 nm diam free‐standing quantum dots have been produced from GaAs/AlGaAs single quantum well material by electron‐beam lithography and low damage electron cyclotron resonance plasma etching. Low‐temperature (5 K) photoluminescence and photoluminescence excitation spectroscopy were used to characterize the material before and after processing into quantum dots. Clear free‐exciton features of linewidth comparable to that obtained from the unprocessed material have been observed in the excitation spectra of the quantum dots. As expected for this size of dot, no significant shift in the wavelength of the luminescence was observed, however, there is an apparent enhancement of the external luminescence efficiency when the geometric fill factor is taken into account. The results also show that luminescence efficiency measurements seeking to identify and elucidate intrinsic 0D effects (i.e., those due to quantum confinement in the active region) should be performed with photoexcitation directly into the active region energy states. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113208

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Erbium surface segregation is observed during growth of Er‐doped Si by molecular beam epitaxy on Si(100) at 600 °C. Once a critical Er surface areal density of 2×1014Er/cm2is reached, enhanced Er trapping is observed, possibly due to the formation of silicide precipitates. Er segregation on Si(100) is fully avoided when growth is performed in an oxygen background pressure of ∼10−10mbar, due to the formation of Er‐O complexes. No Er segregation is observed on Si(111), which is attributed to the formation of epitaxial Er3Si5precipitates. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113209

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The fabrication of nanometer‐scale side‐gated silicon field effect transistors using an atomic force microscope is reported. The probe tip was used to define nanometer‐scale source, gate, and drain patterns by the local anodic oxidation of a passivated silicon (100) surface. These thin oxide patterns were used as etch masks for selective etching of the silicon to form the finished devices. Devices with critical features as small as 30 nm have been fabricated with this technique. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113210

出版商:AIP    

年代:1995

数据来源: AIP