摘要:

In this paper, we examine Si and Te ion implant damage removal in GaN as a function of implantation dose, and implantation and annealing temperature. Transmission electron microscopy shows that amorphous layers, which can result from high-dose implantation, recrystallize between 800 and 1100 °C to very defective polycrystalline material. Lower-dose implants (down to5×1013 cm−2), which are not amorphous but defective after implantation, also anneal poorly up to 1100 °C, leaving a coarse network of extended defects. Despite such disorder, a high fraction of Te is found to be substitutional in GaN both following implantation and after annealing. Furthermore, although elevated-temperature implants result in less disorder after implantation, this damage is also impossible to anneal out completely by 1100 °C. The implications of this study are that considerably higher annealing temperatures will be needed to remove damage for optimum electrical properties. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121030

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Sheet carrier concentrations in quantum wells of InAs clad by AlSb were enhanced by modulation doping with very thin (9–12 Å) remote InAs(Si) donor layers. The growth temperature of the donor layers was a key parameter, with relatively low temperatures required to minimize Si segregation into the AlSb. Sheet carrier concentrations as high as3.2×1012/cm2and5.6×1012/cm2were achieved by single- and double-sided modulation doping, respectively. High electron mobility transistors fabricated using the modulation doped structure exhibited a unity current gain cut-off frequency of 60 GHz for a 0.5 &mgr;m gate length at a source-drain voltage of 0.5 V.

ISSN:0003-6951    

DOI:10.1063/1.121010

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The temperature dependence of the spatial resolution of capacitance-voltage(C−V)profiles in the compositional quantum well (CQW) is investigated. The apparent carrier distribution (ACD) peak in theIn0.2Ga0.8As/GaAssingle QW is observed to show a strong temperature dependence, compared to that in Si &dgr;-doped GaAs. The ACD peak in CQW is wider (narrower) than the spatial extent of ground-state wave function at high (low) temperatures. The self-consistent numerical simulations on the carrier distribution show that the full width at half maximum of ACD peak in CQW is mainly affected by the debye averaging process at high temperatures and the change in the position expectation value of the two-dimensional electrons at low temperatures. This change in the position expectation value is found to be much smaller than the spatial extent of ground-state electron wave function. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121011

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Thin film silicon-on-insulator (SOI) devices have an advantage of excellent isolation due to the buried oxide layer leading to reduced capacitance coupling and no latchup in complementary metal-oxide-silicon circuits compared with bulk silicon devices. Reduced junction area should lead to lower leakage for a given device. However, because of the buried oxide, stress is built up in the Si island during isolation processes, especially near the island edges, inducing new kinds of leakage currents, which are not observed in bulk silicon devices. This letter proposes five leakage current models of the partially depleted SOI devices, identifies their origins, and suggests methods to prevent each type. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121012

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Electron transport properties of double delta-doped GaAs structures based on high electron mobility single delta-doped layers with a sheet concentration of3×1012 cm−2have been investigated for spacer thicknesses up to 1100 Å at 77 and 300 K. At an optimized spacer thickness of about 200 Å, a maximum in conductivity is observed, which exceeds the conductivity of a single delta-doped layer with the same total concentration by 30&percent; and 20&percent; at 300 and 77 K. The mobility and concentration as a function of spacer thickness are also presented and analyzed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121013

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We fabricated a silicon single-electron quantum-dot transistor, which showed drain current oscillations at room temperature. These oscillations are attributed to electron tunneling through a single silicon quantum dot inside a narrow wire channel. Analysis of its current–voltage characteristic indicates that the energy level separation is about 110 meV and the silicon dot diameter is about 12 nm. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121014

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Strained-layer (111)BIn0.2Ga0.8As/GaAsp-i-nquantum well structures grown with exciton transitions well resolved at room temperature have been studied by photoreflectance spectroscopy. Using the reduced mass deduced from experiments, the built-in electric field in the barrier region is obtained from the above band-gap Franz–Keldysh oscillations. The strain-induced piezoelectric field is then determined directly from a comparison of the periods of Franz–Keldysh oscillations in different samples. Numerical solutions for the exciton transitions from the derived potential profiles are in good agreement with the experimental results. The piezoelectric constant is also determined using the piezoelectric field. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121015

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Deep-level transient spectroscopy has been used to characterize electronic defects inn-type GaN grown by reactive molecular-beam epitaxy. Five deep-level electronic defects were observed, with activation energiesE1=0.234±0.006,E2=0.578±0.006,E3=0.657±0.031,E4=0.961±0.026, andE5=0.240±0.012 eV. Among these, the levels labeledE1, E2,andE3are interpreted as corresponding to deep levels previously reported inn-GaN grown by both hydride vapor-phase epitaxy and metal organic chemical vapor deposition. LevelsE4andE5do not correspond to any previously reported defect levels, and are characterized for the first time in our studies. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121016

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Hall-effect measurements were conducted on unintentionally dopedn-type GaN films grown on sapphire substrates by hydride vapor phase epitaxy. Film nucleation involved either a GaCl or ZnO pretreatment. Variable temperature Hall-effect measurements reveal a dependence of both the electron concentration and the Hall mobility on film thickness. We demonstrate that this dependence is indicative of a nonuniform distribution of electrically active defects. For GaCl-pretreated sapphire the presence of a highly conductive, 200-nm-thick near-interface layer is likely to account for the observed phenomena. For ZnO-pretreated sapphire the Hall-effect data clearly indicate a continuous reduction of the defect density with increasing film thickness. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121017

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report a study of electrophotoluminescence in a biased shallowGaAs/AlxGa1−xAs(x=0.04)quantum well. It is shown that photocarriers escape from the well via direct tunneling, resulting in a drastic quenching of the photoluminescence at remarkably low fields(F<10 kV/cm).We develop a simple method to measure the field-induced escape time from a set of cw photoluminescence, photocurrent, and time-resolved photoluminescence experiments. Comparison with a semiclassical model shows that, in this regime, Coulomb interaction affects significantly the single electron direct tunneling scheme. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121018

出版商:AIP    

年代:1998

数据来源: AIP