摘要:

We report the dc and microwave performance ofi‐InAlAs/n+‐InGaAs/i‐InAlAs heterojunction metal‐semiconductor field‐effect transistors (MESFETs) with gate lengths from 0.25 to 0.35 &mgr;m. At 10 GHz, an extrinsic transconductance (gm) of 507 mS/mm, a current gain cutoff frequency (ft) of 49.5 GHz, and a power gain cutoff frequency (fmax) of 70.5 GHz were observed for a 0.25 &mgr;m gate device. For a 0.3 &mgr;m gate device, agmof 545 mS/mm, anftof 42 GHz, and anfmaxof 114 GHz were measured. Output conductance as low as 7.7 mS/mm was measured. The voltage gain for measured devices is well above 20 for a wide range of bias conditions.

ISSN:0003-6951    

DOI:10.1063/1.100740

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

InP solar cells were fabricated from films deposited by metalorganic chemical vapor deposition on Si substrates (using a GaAs buffer layer) and on GaAs substrates. Air mass zero efficiencies of 7.1% and 9.4%, respectively, were achieved. Prospects are good for improving the material quality of the InP films, but more work is needed to make then+‐p‐p+structure of the InP solar cells compatible with the silicon substrates, which causen‐type doping of the III‐V films.

ISSN:0003-6951    

DOI:10.1063/1.100741

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

InAsxP1−x/InP strained quantum well structures have been prepared by atmospheric‐pressure organometallic vapor phase epitaxy (OMVPE). Structures with compositions ofx=0.40–0.67 and quantum well thicknesses of 0.8–16 nm were evaluated using photoluminescence spectroscopy. Strain in the pseudomorphic wells ranged from 1.3 to 2.1%. Doublets and multiplets are observed in the photoluminescence spectra and are attributed to luminescence from regions in the wells differing in thickness by a single monolayer, with atomically smooth interfaces over areas greater in lateral extent than the exciton diameter. Typical full widths at half maximum of the photoluminescence from the thinnest wells are 8–14 meV, comparable to the best reported values for thin lattice‐matched quantum wells prepared from the InGaAs(P)/InP system using OMVPE.

ISSN:0003-6951    

DOI:10.1063/1.100742

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Layer intermixing in MeV Si‐implanted GaAs/AlGaAs superlattices (SLs) with doses between 3×1015and 1×1016/cm2has been examined by transmission electron microscopy and secondary‐ion mass spectrometry. After either rapid thermal annealing at 1050 °C for 10 s or furnace annealing at 850 °C for 3 h, all the SLs showed a highly crystalline, defect‐free zone in the near‐surface region followed by a band of secondary defects, with the maximum density located about 1 &mgr;m below the surface. A totally mixed region, within the secondary defect band, occurred only in the SL implanted to 1×1016Si/cm2and annealed at 850 °C for 3 h. At lower doses or under rapid thermal annealing, only slight Al/Ga interdiffusion was observed, primarily in the layers that contained the high density of dislocation defects. For either annealing condition, the Si concentration profiles showed only slight broadening and they correlated with the distribution of secondary defects as well as with the depth of the intermixed layer. The effects of dynamic annealing and surface on the implantation energy dependence, i.e., MeV vs keV, of layer intermixing are discussed.

ISSN:0003-6951    

DOI:10.1063/1.100743

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Recently, there has been a great deal of interest in Na2S⋅9H2O as a passivating chemical treatment for GaAs surfaces. It has been shown that it reduces the high surface recombination velocity characteristic of GaAs surfaces, and may offer hope for ‘‘unpinning’’ the surface Fermi level. We have used photoemission spectroscopy to study the band bending and chemistry of these overlayers onn‐type GaAs (100). Identically prepared samples show the characteristic increase in the photoluminescence signal, and have also been characterized using surface conductivity measurements. We find using photoemission that the surface Fermi level of the treated wafer is still near midgap. We also observe the chemistry at the interface, and offer a possible explanation of the photoluminescence and surface conductivity data in terms of it and the advanced unified defect model.

ISSN:0003-6951    

DOI:10.1063/1.100744

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

AlGaAs/GaAs single heterojunction bipolar transistors grown on InP substrates by molecular beam epitaxy have been fabricated and tested. An eight‐period 25 A˚/25 A˚ In0.53Ga0.47As/GaAs strained‐layer superlattice is incorporated in the buffer structure to reduce dislocation propagation to the active region. Small‐signal common emitter current gains of about 20 and 30 at a collector current density of 2×103A/cm2have been obtained for devices on InP as compared to about 60 and 150 for those on GaAs in structures with base thickness of 0.12 &mgr;m doped with Be to 1×1019and 1×1018cm−3, respectively. Current densities as high as 1×104A/cm2have been achieved in these devices with emitter area of 50×50 &mgr;m2without degradation, demonstrating the excellent stability of this material. From the collector current dependence of the current gain, ideality factors of 1.3 and 1.2 for the emitter junctions have been obtained for devices on InP and GaAs, respectively.

ISSN:0003-6951    

DOI:10.1063/1.100745

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

For the first time, {111} ordering (CuPt type) has been observed in InAs1−xSbxalloys in a wide compositional range fromx=0.22 to 0.88. The order‐induced spots show the highest intensity forx≊0.5 samples and the lowest intensity toward each binary end compound. Only two of the four variants are formed during growth. In some areas the degree of order for these two variants is equal, and in other areas one variant dominates.

ISSN:0003-6951    

DOI:10.1063/1.100746

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A three‐terminaln+‐i‐&dgr;p+‐i‐n+bipolar–unipolar transition transistor has been successfully fabricated by molecular beam epitaxy. Due to the combination of the two transitions, they make a genuine N‐shaped current‐voltage characteristic. It is a voltage‐controlled device with a variable peak‐to‐valley current ratio which is adjustable by a bias applied to the third terminal (base). A hypothetical model is proposed and confirmed by experiments.

ISSN:0003-6951    

DOI:10.1063/1.100747

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A standard 600 °C closed‐tube Zn diffusion into an unstrained InP/In0.53Ga0.47As superlattice was found to produce new superlattices containing Zn3P2layers, and in some cases Zn3As2layers. Crystalline properties and diffusion profiles were examined by transmission electron microscopy and secondary‐ion mass spectrometry. Initial doping of Zn enhances the diffusion of In and Ga and results in a superlattice of uniform In and Ga distribution. Upon further infusion of Zn, Zn3P2forms selectively in the phosphorus layers and propagates from the surface while maintaining an atomically abrupt Zn3P2/In1−xGaxP interface. Zn3As2conversion is also observed to occur under sufficiently stringent conditions. Diffusion of P and As was not observed.

ISSN:0003-6951    

DOI:10.1063/1.101480

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have found thatinsitusuperconducting Y‐Ba‐Cu‐O thin films can be produced by sputtering without the aid of any external O2source during deposition. The films were produced by rf magnetron sputtering from a composite target onto MgO(100) substrates heated at 650 °C. Films made in a pure Ar pressure of 24 mTorr and fast cooled in N2ambient contain the tetragonal YBa2Cu3Oxphase withxestimated to be 6.1. Films made under the same sputtering conditions but cooled in 30 mTorr oxygen after deposition, show a superconducting transitionTc(R=0) at 71 K with an onset at 85 K. TheTc(R=0) rises to 80 K if 0.5 mTorr oxygen was added during sputtering. The experimental results provide conclusive evidence that sufficient oxygen can be incorporated into the films to form the tetragonal YBa2Cu3Oxphase simply by physical sputtering from an oxide target. The films absorb additional oxygen and transform into the orthogonal, superconducting phase when subsequently cooled in partial O2.

ISSN:0003-6951    

DOI:10.1063/1.101560

出版商:AIP    

年代:1989

数据来源: AIP