摘要:

We show that photorefractive beam coupling gain as a function of grating period measured in semi‐insulating GaAs with an external ac electric field or with a dc field and moving fringes can be explained theoretically by a mobility‐lifetime product about four orders of magnitude smaller than that obtained in low‐field conditions. This reduction is caused by enhanced occupation of theLband at high fields coupled with the lowLband mobility and by the increase in recombination due to the cascade capture process that occurs for electric fields above a few kV/cm.

ISSN:0003-6951    

DOI:10.1063/1.102786

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

High quality, coherently strained Si1−xGexalloy layers are studied using high‐resolution x‐ray diffraction (HRXRD) andexsitutransmission electron diffraction. Several samples were grown at extremely low temperatures (310–330 °C) by molecular beam epitaxy. Sample thicknesses and alloy concentrations were chosen to span a range beginning just below to significantly above critical thicknesses previously reported for this system. HRXRD observations demonstrate a high degree of coherency in the as‐grown structures since measurements of the lattice constant parallel to the sample surface (a∥) consistently yield the value for the (100)Si substrate. HRXRD from (004) planes used to measurea⊥typically yield a spectrum with several peaks for growths in excess of the critical thickness and single peaks for those below the critical thickness. The high degree of coherency observed in these samples suggests that chemical segregation is responsible for the observed x‐ray peaks.

ISSN:0003-6951    

DOI:10.1063/1.102787

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A model is presented which accounts for the anomalous diffusion of thep‐type base dopant during the growth of AlGaAs‐GaAsnpnbipolar transistors. The model is based upon Fermi level pinning at the crystal surface during epitaxial growth which leads to an increased concentration of column III interstitial defects in heavilyn‐type AlGaAs or GaAs. The excess column III interstitials generated in then‐type crystal flow into thep+base region causing a transfer of thep‐type impurity atoms from column III lattice sites to interstitial positions through a ‘‘kick‐out’’ mechanism. Once in interstitial positions the impurity atoms are known to diffuse rapidly. The model is consistent with previously proposed mechanisms for both impurity diffusion and column III self‐diffusion.

ISSN:0003-6951    

DOI:10.1063/1.102788

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The use of a Si0.7Ge0.3strained layer as an etch stop in silicon‐based materials is reported. The etch rates were characterized through silicon and a 60 nm Si0.7Ge0.3strained layer. The etch rate through undoped silicon was 17–20 nm/min, while the etch rate through the Si0.7Ge0.3layer was 1 nm/min. After annealing the wafer to 850 °C for 30 min, transmission electron microscopy was used to show that strain in the alloy layer was only partially relieved, and that generated misfit dislocations were confined to the strained Si0.7Ge0.3layer. The etch rate through the strained layer increased to 1.7 nm/min after this treatment, and was still perfectly functional as an etch stop.

ISSN:0003-6951    

DOI:10.1063/1.102789

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Electrical and optical properties of antiphase domain boundaries (APBs) in GaAs epitaxial layers grown on Si substrates have been investigated using cathodoluminescence, electron beam induced current, and scanning deep level transient spectroscopy. It was found that APBs reduce near‐band‐gap luminescence and minority‐carrier lifetime. In contrast to recombination at threading dislocations in GaAs films, the nonradiative recombination processes at APBs are not due to deep traps but rather to a continuum of band‐gap states introduced by APBs.

ISSN:0003-6951    

DOI:10.1063/1.102790

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report the first demonstration of metal‐semiconductor field‐effect transistors (MESFETs) made from GaAs structures grown with an alkylarsine source, tertiarybutylarsine (t‐BuAsH2). MESFET fabrication was performed in parallel ont‐BuAsH2and arsine‐grown wafers to enable direct comparison of device characteristics. The GaAsn+‐nMESFETs made witht‐BuAsH2exhibited excellent saturation and pinch‐off characteristics, and diode performance comparable to arsine‐grown devices. Although the peak transconductancegmwas lower than that achieved with the arsine sample, the form of thegmversus gate voltage curves for thet‐BuAsH2‐grown devices were characteristic of well‐behaved GaAs MESFETs. These initial results demonstrate the capability oft‐BuAsH2for growing electronic device structures having good carrier transport properties and effective isolation layers.

ISSN:0003-6951    

DOI:10.1063/1.102791

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Successful growth of lattice‐matched Sc1−xErxAs layers buried in GaAs with a room‐temperature resistivity of ∼50 &mgr;&OHgr; cm demonstrates the feasibility of fabricating heterostructures of lattice‐matched rare‐earth monopnictides and monochalcogenides in semiconductors. Reflection high‐energy electron diffraction oscillations during ScAs, ErAs, and Sc1−xErxAs growth indicate monolayer‐by‐monolayer growth.

ISSN:0003-6951    

DOI:10.1063/1.102792

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Electron focusing effect is observed in a two‐dimensional electron gas using samples with simple multiparallel one‐dimensional channels made by a Be focused ion beam (FIB). Subharmonics and harmonics are resolved; their strengths allow a direct determination of the elastic scattering lengthle=1.8 &mgr;m and the specularity coefficientp=0.35 for electron reflection at the boundary defined by the FIB. The temperature dependence of the focusing effect is much weaker than the Shubnikov–de Haas effect.

ISSN:0003-6951    

DOI:10.1063/1.102793

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We propose and demonstrate an all‐epitaxial semiconductor/semimetal Schottky (S3) photodiode based on ann‐type Hg0.56Cd0.46Te/HgTe isotype heterojunction. The structure, grown using molecular beam epitaxy, was fabricated into back‐illuminated mesa diodes. A 40‐&mgr;m‐diam photodiode shows room‐temperature rectification and high efficiency photoresponse, with a long‐wavelength cutoff of 2.43 &mgr;m and a peak quantum efficiency of 44% at 2.0 &mgr;m for 250 mV of reverse bias. The dark current at this bias is 100 &mgr;A.

ISSN:0003-6951    

DOI:10.1063/1.102794

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For a variety of device applications, junction devices in particular, we have demonstrated a heterostructure system of Y1Ba2Cu3O7−y/Y1−xPrxBa2Cu3O7−ywhich maintains epitaxy over the entire Pr composition rangex=0–1. We have grown both trilayer and multiperiod superlattices which show nearly single crystalline helium ion backscattering minimum yields of <6% in the topmost layer. X‐ray diffraction measurements indicatec‐axis orientation by a transverse scan across (005) line with a full width at half maximum of 0.6° and 0.4° on MgO and SrTiO3substrates, respectively. Scanning Auger electron depth profiles and cross‐sectional transmission electron micrographs indicate abrupt Pr/Y interfaces within one unit cell and virtually no disruption of the layered structure at the interface. These results indicate the potential for the growth of excellent heterostructures and superlattices of the high‐temperature superconductors.

ISSN:0003-6951    

DOI:10.1063/1.103291

出版商:AIP    

年代:1990

数据来源: AIP