Normally-off metamorphic AlInAs/AlInAs HEMTs on Si substrates grown by MOCVD

A combination of self-aligned fluoride-based plasma treatment and post-gate rapid thermal annealing was developed to fabricate a novel 120-nm T-shaped gate normally-off metamorphic Al0.49In0.51As/Ga0.47In0.53 As HEMT device on a Si substrate grown by metal-organic chemical vapor deposition(MOCVD). A shift of the threshold voltage, from-0.42 V to 0.11 V was obtained and the shift can be effectively adjusted by the process parameter of CF4 plasma treatment. Furthermore, a side benefit of reducing the leakage current of the device up to two orders of magnitude was also observed.E-mode transistors with 120 nm gate length own fTup to 160 GHz and fmax of 140 GHz. These characteristics imply the potential of the fluoride-based plasma treatment technology for the fabrication of monolithic enhancement/depletion-mode m HEMTs, which also encourage the massive production with this low-cost technology.     

XPS data for sputter-cleaned In0.53Ga0.47As,GaAs, and InAs surfaces

Core level binding energies and Auger parameters were determined for In, Ga, and As in the three compounds In_0.53Ga_0.47As, GaAs, and InAs. The surfaces were cleaned by 1.5 keV Ar ion bombardment. Under this condition the radiation-induced defects are small. In the case of GaAs the Ga and As3d levels become comparable with available data for chemically cleaned surfaces. The high Ga deficiency of chemically cleaned In_0.53Ga_0.47As surfaces could not be observed. Sputter cleaned surfaces seem to be closer to the bulk composition.     

Numerical study of strained InGaAs quantum well lasers emitting at 2.33 μm using the eight-band model

We investigate the band structure of a compressively strained In(Ga)As/In 0.53 Ga 0.47 As quantum well (QW) on an InP substrate using the eight-band k · p theory.Aiming at the emission wavelength around 2.33 μm,we discuss the influences of temperature,strain and well width on the band structure and on the emission wavelength of the QW.The wavelength increases with the increase of temperature,strain and well width.Furthermore,we design an InAs /In 0.53 Ga 0.47 As QW with a well width of 4.1 nm emitting at 2.33 μm by optimizing the strain and the well width.     

Structural and electronic properties of group III Rich In0.53Ga0.47As(001)

The structural and electronic properties of group III rich In_0.53Ga_0.47As(001) have been studied using scanning tunneling microscopy/spectroscopy (STM/STS). At room temperature (300 K), STM images show that the In_0.53Ga_0.47As(001)–(4 × 2) reconstruction is comprised of undimerized In/Ga atoms in the top layer. Quantitative comparison of the In_0.53Ga_0.47As(001)–(4 × 2) and InAs(001)–(4 × 2) shows the reconstructions are almost identical, but In_0.53Ga_0.47As(001)–(4 × 2) has at least a 4× higher surface defect density even on the best samples. At low temperature (77 K), STM images show that the most probable In_0.53Ga_0.47As(001) reconstruction is comprised of one In/Ga dimer and two undimerized In/Ga atoms in the top layer in a double (4 × 2) unit cell. Density functional theory (DFT) simulations at elevated temperature are consistent with the experimentally observed 300 K structure being a thermal superposition of three structures. DFT molecular dynamics (MD) show the row dimer formation and breaking is facilitated by the very large motions of tricoodinated row edge As atoms and z motion of In/Ga row atoms induced changes in As–In/Ga–As bond angles at elevated temperature. STS results show there is a surface dipole or the pinning states near the valence band (VB) for 300 K In_0.53Ga_0.47As(001)–(4 × 2) surface consistent with DFT calculations. DFT calculations of the band-decomposed charge density indicate that the strained unbuckled trough dimers being responsible for the surface pinning.     

Sequence influence of nonidentical InGaAsP quantum wells on broadband characteristics of semiconductor optical amplifiers--superluminescent diodes

Extremely broadband emission is obtained from semiconductor optical amplifiers-superluminescent diodes with nonidentical quantum wells made of InGaAsP/InP materials. The well sequence is experimentally shown to have a significant influence on the emission spectra. With the three In(0.67) Ga(0.33) As(0.72) P(0.28) quantum wells near the n -cladding layer and the two In(0.53) Ga(0.47) As quantum wells near the p -cladding layer, all bounded by In(0.86) Ga(0.14) As(0.3)P(0.7) barriers, the emission spectrum could cover from less than 1.3 to nearly 1.55 microm, and the FWHM could be near 300 nm.     

Probing the plateau-insulator quantum phase transition in the quantum hall regime

We report quantum Hall experiments on the plateau-insulator transition in a low mobility In(0.53)Ga(0.47)As/InP heterostructure. The data for the longitudinal resistance rho(xx) follow an exponential law and we extract a critical exponent kappa = 0.55+/-0. 05 which is slightly different from the established value kappa = 0. 42+/-0.04 for the plateau transitions. Upon correction for inhomogeneity effects, which cause the critical conductance sigma(*)(xx) to depend marginally on temperature, our data indicate that the plateau-plateau and plateau-insulator transitions are in the same universality class.     

Determination of breakdown voltage of In_(0.53)Ga_(0.47)As/InP single photon avalanche diodes

We examine the saturation of relative current gain of In0.53 Ga0.47As/InP single photon avalanche diodes(SPADs) operated in Geiger mode.The punch-through voltage and breakdown voltage of the SPADs can be measured using a simple and accurate method.The analysis method is temperature-independent and can be applied to most SPADs.     

Nanoelectronic devices---resonant tunnelling diodes grown on InP substrates by molecular beam epitaxy with peak to valley current ratio of 17 at room temperature

This paper reports that InAs/In$_{0.53}$Ga$_{0.47}$As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm$^{2}$ has been obtained for diodes with AlAs barriers of ten monolayers, and an In$_{0.53}$Ga$_{0.47}$As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.     

Synchrotron radiation photoemission study of interface formation between MgO and the atomically clean In0.53Ga0.47As surface

The evolution of interface formation between MgO and the atomically clean In_0.53Ga_0.47As is studied by synchrotron radiation based photoemission. The deposition of MgO in a step wise fashion on the decapped In_0.53Ga_0.47As surface at room temperature results in the growth of an ultrathin interfacial oxide layer. Subsequent thermal annealing at 400 °C led to the reduction of the As and In oxides and the appearance of a Ga oxide component. The deposition of metallic Mg resulted in the further removal of the interfacial oxide and the out diffusion of In into the overlayer indicating severe disruption of the interface. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of Nonequilibrium LO Phonons on High-frequency Performance of One-dimensional Hot Electrons in Quantum Wires of Polar Semiconductors

Small-signal ac transport of degenerate one-dimensional hot electrons in quantum wires of GaAs and In_0.53Ga_0.47As is studied for lattice temperatures of 77 K and 300 K. The carrier energy loss via polar optic phonons and momentum losses via polar optic phonons, acoustic phonons and ionized impurities are included in the calculations. Alloy disorder scattering in momentum loss is additionally incorporated for (In,Ga)As. The consideration of nonequilibrium optical phonons or hot phonons is found to enhance the 3dB cut-off frequency (f_3dB) considerably, where the ac mobility falls to 0.707 of its low frequency value. f_3dB is generally higher for (In,Ga)As quantum wire than for GaAs.     

Ion-irradiated In0.53Ga0.47As photoconductive antennas for THz generation and detection at 1.55 μm wavelength

We present a detailed study of the photoconductive antennas made from heavy-ion-irradiated In_0.53Ga_0.47As material. The optical and transport properties of ion-irradiated In_0.53Ga_0.47As material are characterized. The terahertz waveforms emitted and detected by ion-irradiated In_0.53Ga_0.47As photoconductive antennas excited by 1.55 μm wavelength femtosecond laser pulses are reported and the effect of the carrier lifetime on the terahertz signal characteristics emitted by such devices is analysed. The performances of ion-irradiated In_0.53Ga_0.47As photoconductive antennas excited by 1.55 μm and also by 0.8 μm wavelength femtosecond laser pulses are compared to those of similar low-temperature-grown GaAs photoconductive antennas. To cite this article: J. Mangeney, P. Crozat, C. R. Physique 9 (2008).     

Direct measurement of the binding energy and bohr radius of a single hydrogenic defect in a semiconductor quantum well

Low-temperature scanning tunneling spectroscopy under ultrahigh vacuum was used to study donor point defects located at the epitaxial surface of an In(0.53)Ga(0.47)As quantum well. The electronic local density of states was measured with nanoscale resolution in the vicinity of single defects. In this way, both the binding energy and the Bohr radius of the defects could be determined. The binding energy and the Bohr radius were found to be functions of the quantum well thickness, in quantitative agreement with variational calculations of hydrogenic impurity states.     

Interdiffused InGaAs/InP quantum wells for polarization-independent electroabsorption

The interdiffusion of In0.53Ga0.47As/InP quantum well structures is presented as an approach for achieving polarization-independent electroabsorption. By considering different interdiffusion rates on group III and group V sublattices, the TE and TM absorption coefficient spectra calculated for the interdiffused InGaAs/InP quantum well show that with a suitable interdiffusion process the tensile strain induced in the interdiffused quantum well can provide polarization-independent absorption properties. For the quantum well structure and interdiffusion process considered here polarization-independent electroabsorption can be achieved around 1.3 μm, which is of considerable interest for optical switching and modulating devices. This revised version was published online in November 2006 with corrections to the Cover Date.     

Rashba spin-orbit coupling probed by the weak antilocalization analysis in InAlAs/InGaAs/InAlAs quantum wells as a function of quantum well asymmetry

We have investigated the values of the Rashba spin-orbit coupling constant alpha in In(0.52)Al(0.48)As/In(0.53)Ga(0.47)As/In(0.52)Al(0.48)As quantum wells using the weak antilocalization (WAL) analysis as a function of the structural inversion asymmetry (SIA) of the quantum wells. We have found that the deduced alpha values have a strong correlation with the degree of SIA of the quantum wells as predicted theoretically. The good agreement between the theoretical and experimental values of alpha suggests that our WAL approach for deducing alpha values provides a useful tool in designing future spintronics devices that utilize the Rashba spin-orbit coupling.     

平面型大光敏元InGaAs线列探测器及其应用

采用晶格匹配的平面型InP／In瞄。Ga叫,As／InP外延材料,设计了一种大光敏元、带有保护环的InGaAs线列探测器。通过I—V9n,4试、扫描电容显微技术（SCM）测试,研究并确定了线列器件的盲元与保护环结构之间的关系。通过设计改进,解决了器件的盲元问题。24×1InGaAs线列短波红外探测在室温20℃、-10mV偏压下,暗电流密度约5nA／cm2。将光敏芯片密封在集成了热电制冷器（TEC）的金属管壳内,组件工作温度5℃,探测器响应光谱在1．0肚m～1．67肚m范围,平均峰值电流响应率为1．3A／W,平均峰值探测率为3．4×10他cm·Hz1/2／W,响应的非均匀性为1．5％。探测器经历一定条件的可靠性筛选试验后,性能未发生明显变化,并进行了航空机载成像应用,成像图片清晰。     

Thermal conductivity reduction and thermoelectric figure of merit increase by embedding nanoparticles in crystalline semiconductors

Atomic substitution in alloys can efficiently scatter phonons, thereby reducing the thermal conductivity in crystalline solids to the "alloy limit." Using In0.53Ga0.47As containing ErAs nanoparticles, we demonstrate thermal conductivity reduction by almost a factor of 2 below the alloy limit and a corresponding increase in the thermoelectric figure of merit by a factor of 2. A theoretical model suggests that while point defects in alloys efficiently scatter short-wavelength phonons, the ErAs nanoparticles provide an additional scattering mechanism for the mid-to-long-wavelength phonons.     

Evolution of surface morphology and photoluminescence characteristics of 1.3-μm In0.5Gao.5As/GaAs quantum dots grown by molecular beam epitaxy

Evolution of surface morphology and optical characteristics of 1.3-μm In0.5Gao.5As/GaAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) are investigated by atomic force microscopy (AFM) and photoluminescence (PL). After deposition of 16 monolayers (ML) of In0.5Ga0.5As, QDs are formed and elongated along the [110] direction when using sub-ML depositions, while large size InGaAs QDs with better uniformity are formed when using ML or super-ML depositions. It is also found that the larger size QDs show enhanced PL efficiency without optical nonlinearity, which is in contrast to the elongated QDs.     

InGaAs/InP heterojunction-channel tunneling field-effect transistor for ultra-low operating and standby power application below supply voltage of 0.5 V

An In_0.53Ga_0.47As/InP heterojunction-channel tunneling field-effect transistor (TFET) with enhanced subthreshold swing (S) and on/off current ratio (I_on/I_off) is studied. The proposed TFET achieves remarkable characteristics including S of 16.5 mV/dec, on-state current (I_on) of 421 μA/μm, I_on/I_off of 1.2 × 10¹² by design optimization in doping type of In_0.53Ga_0.47As channel at low gate (V_GS) and drain voltages (V_DS) of 0.5 V. Comparable performances are maintained at V_DS below 0.5 V. Moreover, an extremely fast switching below 100 fs is accomplished by the device. It is confirmed that the proposed TFET has strong potentials for the ultra-low operating power and high-speed electron device.     

Growth of catalyst-free GaAs nanowire with As pulse injection for full zinc-blende structure

Full zinc-blende structure GaAs nanowire grown by a catalyst-free method is reported with As pulse injection in the initial growth time. When As is injected by a pulse while maintaining Ga injection, high Ga supersaturation could easily form nanowire nucleation for the seed formation. Then, continuous GaAs injection contributes to GaAs nanowire growth for increasing length. The GaAs nanowire could grow further with 3.7-μm length and 120-nm diameter. GaAs nanowires were measured by transmission electron microscopy analysis.     

InP-based InGaAs/InAlGaAs digital alloy quantum well laser structure at 2 μm

The structural and optical characteristics of InP-based compressively strained InGaAs quantum wells have been significantly improved by using gas source molecular beam epitaxy grown InAs/In 0.53 Ga 0.47 As digital alloy triangular well layers and tensile In 0.53 Ga 0.47 As/InAlGaAs digital alloy barrier layers.The x-ray diffraction and transmission electron microscope characterisations indicate that the digital alloy structures present favourable lattice quality.Photoluminescence (PL) and electroluminescence (EL) measurements show that the use of digital alloy barriers offers better optical characteristics than that of conventional random alloy barriers.A significantly improved PL signal of around 2.1 μm at 300 K and an EL signal of around 1.95 μm at 100 K have been obtained.