MOVPE InGaAs/InP grown directly on GaAs substrates

We have demonstrated the feasibility of growth of InP/InGaAs structures directly on GaAs using atmospheric pressure metal organic vapour phase epitaxy. Growth conditions and the equipment used are described along with some preliminary measurements on the GaAs/InP/InGaAs wafers. P-N junctions were formed in these materials to evaluate diode characteristics.     

Processing aspects in the low-frequency noise of nMOSFETs on strained-silicon substrates

The impact of different processing factors on the low-frequency (LF) noise of nMOSFETs fabricated in strained-silicon (SSi) substrates will be described. It is shown that the use of an SSi substrate can yield improved LF noise performance compared with standard Czochralski silicon material. This is demonstrated for both full-wafer and selective epitaxial SSi material. The lower 1/f noise points to an improved gate oxide quality, i.e., with a lower interface and bulk defect density, and is correlated with the low-field mobility or transconductance of the transistors. At the same time, it will be demonstrated that there exist defect-related LF noise mechanisms, which generally give rise to excess generation-recombination (GR) noise. Associated with this GR noise, a degradation of either the OFF-state leakage current or the mobility (transconductance) of the devices is observed. It is clear that noise is a sensitive parameter to local defectiveness and may be a useful tool for both materials' characterization and the analysis of processing-related device degradation mechanisms.     

GaAs MESFETs on InP substrates grown using chloride close-proximityreactor system

DC and microwave characteristics of GaAs metal-semiconductor field-effect transistors (MESFETs) on InP grown using the chloride close-proximity reactor (CPR) system are reported. The FETs have an extrinsic maximum transconductance of 210 mS/mm for a drain saturation current of 110 mA/mm, a cutoff frequency of unity current gain of 13 GHz, and a maximum frequency of oscillation of 21 GHz. The dislocation density in a 1.6-μm GaAs layer on InP is 10⁸ cm^-2 measured from cross-sectional transmission electron microscopy (TEM). The full width at half maximum of (400) reflection is 270" for a 3-μm-thick GaAs layer     

Photoluminescence characterization of solution and lec grown InP

Low temperature photoluminescence and electrical measurements on bulk grown polycrystalline and single crystal InP indicate the purity and crystal perfection to be equivalent to that of LPE and VPE samples. This work was supported in part by the U.S. Army Research Office, Research Triangle Park, N.C.; Defense Research Projects Agency, Arlington, VA; and Rome Air Development Center, Hanscom Air Force Base, Massachusetts.     

GaInAs/InP quantum wires grown by metalorganic vapor phase epitaxy on V-grooved InP substrates

A single nominally lattice matched GaInAs quantum well (QW)/quantum wire (QWR) structure was grown by metalorganic vapor phase epitaxy (MOVPE) in V-grooved InP substrates. Different Si0₂ etch masks with opening widths from 2 μm down to 200 nm (for application as second order DFB grating) were defined by optical and electron beam lithography. A damage-reduced wet chemical etching process enables the growth of the GaInAs QWs/QWRs without any InP buffer layer. In low temperature photoluminescence we found improved intensity for all wire structures prepared by this etching technique. A reduction of the period and opening width of the V-groove etch mask resulted in a optimized luminescence intensity ratio between QW and QWR. Decay times from time resolved luminescence measurements were compared to the decay times of wet or dry etched mesa wires before and after regrowth. The good optical properties of the GaInAs QWRs are encouraging for future application as a QWR-laser device.     

Single-mode InGaAsP/InP buried waveguide structures grown on channelled {111}B InP substrates

InGaAsP buried waveguide structures were fabricated by LPE on channelled {111}B InP substrates. Control of the channel depth and growth time enabled waveguides of small dimensions to be produced which supported one TE and one TM polarised mode only.     

Growth and characterizations of InP self-assembled quantum dots embedded in InAIP grown on GaAs substrates

We report the characteristics of InP self-assembled quantum dots embedded in In_0.5Al_0.5P on GaAs substrates grown by metalorganic chemical vapor deposition. The InP quantum dots show increased average dot sizes and decreased dot densities, as the growth temperature increases from 475°C to 600°C with constant growth time. Above the growth temperature of 600°C, however, dramatically smaller and densely distributed self-assembled InP quantum dots are formed. The small InP quantum dots grown at 650°C are dislocation-free “coherent” regions with an average size of ∼20 nm (height) and a density of ∼1.5 × 10⁸ mm⁻². These InP quantum dots have a broad range of luminescence corresponding to red or organge in the visible spectrum.     

Low-frequency noise behavior of 0.15-μm gate-lengthlattice-matched and lattice-mismatched MODFETs on InP substrates

Experimental data are presented on equivalent gate noise voltage from 1 to 10⁵ Hz obtained from lattice-matched and strained InGaAs quantum-well modulation-doped field effect transistors (MODFETs). In both types of devices excess generation-recombination (g-r) noise is observed at or below 100 Hz above an `apparent' background 1/f noise with spectral intensity ranging from 0.5×10^-17 to 2×10^-17 V²-Hz^-1-cm² at 1 Hz. These results are comparable to those reported by S.M.J. Liu et al. (1986) for the pseudomorphic MODFETs     

Photoluminescence and raman scattering characterization of silicon-doped In0.52Al0.48As grown on InP (100) substrates by molecular beam epitaxy

Growth of In_0.52Al_0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different silicon doping levels is carried out. The doped samples show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. There is a reduction in both the AlAs-like and InAs-like longitudinal-optic (LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased. The PL intensity also showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.     

Static and low-frequency noise characterization in submicron MOSFETs for memories cells applications

In this paper, we present the extraction of oxide traps properties of n-metal-oxide-semiconductor (N-MOS) field effect transistors with W×L=0.5×0.1 μm² using low-frequency (LF and random telegraph signal) noise and static I(V) characterizations. The impact of oxide thickness, on static and noise parameters is analyzed. Static measurements on N-MOS devices with different tunnel oxide thickness show anomalies (a significant increase in V_t values for low temperature and kink effect) attributed to traps located in the oxide. From LF noise analysis we find that 1/f noise stems from carrier number fluctuations. The slow oxide trap concentration deduced from the noise data is about 10¹⁵ eV/cm³ in agreement with the state-of-the-art gate oxides. Finally, drain current RTS amplitude as large as 10% have been observed.     

In situ observation of surface morphology of InP grown on singular and vicinal (001) substrates

Surface morphology of InP layers is monitored during organometallic vapor phase epitaxy using an in situ diffuse laser light scattering technique. Changes in the diffuse scatter signal are noted for several substrate orientations near the (001) plane and at various growth temperatures. The diffuse scatter signal is shown to be a semi-quantitative indicator of surface roughness through post-growth examination of the samples with phase contrast optical microscopy and atomic force microscopy. Singular substrates consistently have almost featureless surfaces and very little diffuse scattering during growth. Vicinal substrates display a more complicated morphological evolution which cannot be deduced from the diffuse scattering alone but which does produce characteristic changes in diffuse scattering.     

Growth and characterization of totally relaxed InGaAs thick layers on strain-relaxed paramorphic InP substrates

In this paper, we present a technological process that can be used to prepare strain-relaxed InAsP/InGaAs bilayer membranes, 0.8% lattice mismatched to InP substrates, with diameters up to 300 μm. It is shown that high-quality thick In_0.65Ga_0.35As layers can be grown fully relaxed on these membranes, without any structural defect, as demonstrated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoluminescence (PL) characterizations. The critical thickness of InAs layers grown on InAs_0.25P_0.75 templates is enhanced from 15 ? to 60 ? when compared to InP substrates.     

InGaAsP/InP BH lasers on p-type InP substrates

A 1.55 ?m InGaAsP/InP BH laser is achieved on a p-type InP substrate resulting in a simple fabrication process. A threshold current as low as 40 mA under CW operation and a pulsed power rating of several hundred mW at 8 A peak current are achieved in buried-heterostructure lasers.     

Improved correlation measurements using voltage and transimpedanceamplifiers in low-frequency noise characterization of bipolartransistors

A method is presented to improve accuracy in low-frequency noise characterization of bipolar transistors by using both a voltage amplifier and transimpedance amplifiers     

Optical and electrical characterization of GaN layers grown on silicon and sapphire substrates

Characterization of the structural, optical and electrical properties of GaN layers grown by two epitaxial techniques (ECR-MBE and MOCVD) using different substrates (vicinal Si111 and sapphire) has been performed. The quality of the samples grown by MOCVD seems to be influenced by the nitrogen source used for the growth. Unintentionally doped MBE samples with n-type concentrations around 10¹⁸ cm⁻³ and Hall mobility of 15 cm² (V s)⁻¹ were studied. GaN films doped with Mg and grown using AlN buffer layers have also been analyzed to study the influence of the thickness of the buffer layer on the optical properties of the GaN epilayer. In the samples with low Mg doping, a thin AlN buffer layer improved the optical quality of the film. In general, all the MBE samples doped with Mg were highly resistive, probably due to a low activation or high ionization energy of the Mg acceptors. Technological issues related to the formation of ohmic contacts on GaN layers are also presented.     

Modeling and characterization of SiGe HBT low-frequency noise figures-of-merit for RFIC applications

We present the first systematic experimental and modeling results of noise corner frequency (f/sub C/) and noise corner frequency to cutoff frequency ratio (f/sub C//f/sub T/) for SiGe heterojunction bipolar transistors (HBTs) in a commercial SiGe RF technology. The f/sub C/ and f/sub C//f/sub T/ ratio are investigated as a function of operating collector current density, SiGe profile, breakdown voltage, and transistor geometry. We demonstrate that both the f/sub C/ and f/sub C//f/sub T/ ratio can be significantly reduced by careful SiGe profile optimization. A comparison of the f/sub C/ and f/sub C//f/sub T/ ratio for high breakdown and standard breakdown voltage devices is made. Geometrical scaling data show that the SiGe HBT with A/sub E/=0.5/spl times/2.5 /spl mu/m/sup 2/ has the lowest f/sub C/ and f/sub C//f/sub T/ ratio compared to other device geometries. An f/sub C/ reduction of nearly 50% can be achieved by choosing this device as the unit cell in RF integrated-circuit design.     

GaAs MESFET's fabricated on InP substrates

This paper reports the first successful MESFET fabrication in GaAs layers grown directly on InP substrates by molecular beam epitaxy (MBE). The fabricated GaAs MESFET's exhibit good I-V curves with complete pinch-off and saturation characteristics. About 100-mS/ mm transconductance was obtained for a 1.2-µm gate length device.     

Growth by selective area epitaxy on patterned substrates and characterization of GaInAs/InP nanostructures

GaInAs/InP multilayer structures have been grown by chemical beam epitaxy in windows opened in Si0₂ masks deposited on (001) InP substrates. The windows were narrow lines of width varying between 20 and 2μm, oriented along the [011_] direction. The growth conditions, substrate temperature and V/III ratio were adjusted to minimize the growth on the masked areas and to create (111) facets along the mesa. The samples were studied using a field emission scanning electron microscope and by low temperature photoluminescence. The diffusion of In and Ga species from the (111) planes towards (100) observed for the growth of InP and GaInAs enhances the growth rate on the (100) plane and changes the composition of the ternary layer. This gives rise to a red shift of the photoluminescence spectra from the GaInAs layers that depends on the initial width of the line. This diffusion can be used to design crescent quantum wires or nanodevices whose band gap varies with the width of the line.     

Structural and optical characterization of InP/GalnP islands grown by solid-source MBE

We report on the growth of InP/GalnP islands on GaAs substrates by solidsource molecular beam epitaxy. It is shown by reflection high energy electron diffraction and atomic force microscopy that a rapid change from a twodimensional to a three-dimensional growth mode occurs at about nominally 1.5 monolayers (MLs) InP. Transmission electron microscopy measurements demonstrate the coherent incorporation of InP islands in an GalnP matrix for nominally 2.5 MLs InP. The energy of the InP photoluminescence (PL) shifts to lower energies (100 meV) when the growth interruption time between the island and cap layer growth is increased from 1 to 300 s in case of nominally 3 MLs InP. Simultaneously, an increase of the PL linewidth is observed from 30 to 60 meV. Room temperature photoreflectance measurements on samples with various InP thickness have been performed. Compared to PL measurements, an additional feature in the photoreflectance spectra is observed for samples with more than 7 MLs InP, which is attributed to a transition between excited electron and hole states of the islands.     

Self-organization phenomenon of strained InGaAs on InP (311) substrates grown by metalorganic vapor phase epitaxy

We have demonstrated that a self-organization phenomenon occurs in strained InGaAs system on InP (311) substrates grown by metalorganic vapor phase epitaxy. This suggests that a similar formation process of nanocrystals exists not only on the GaAs (311)B substrate but also on the InP (311)B substrate. However, the ordering and the size homogeneity of the self-organized nanocrystals are slightly worse than those of the InGaAs/AlGaAs system on the GaAs (311)B substrate. The tensilely strained condition of a InGaAs/InP system with growth interruption in a PH₃ atmosphere reveals a surface morphology with nanocrystals even on the InP (100) substrate. It was found that strain energy and high growth temperature are important factors for self-organization on III-V compound semiconductors. Preliminary results indicate that the self-organized nanostructures in strained InGaAs/InP systems on InP substrates exhibit room temperature photoluminescent emissions at a wavelength of around 1.3 p.m.